Tetrahedron Letters

Editorial board ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42
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Graphical Contents List ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42
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Isoquinoline skeleton synthesis via chelation-assisted C−H activation ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Ruoyu He , Zhi-Tang Huang , Qi-Yu Zheng , Congyang Wang Transition-metal-catalyzed isoquinoline synthesis that profits from the strategy of chelation-assisted C−H activation has flourished over the past decade. By virtue of the directed C−H bond cleavage of imines, amines, amidines, oximes, hydroximoyl halides, hydrazones, or azines, diverse isoquinoline derivatives have been accessed from alkynes, conjugated dienes, or diazo compounds under the catalysis of rhodium, ruthenium, palladium, nickel, or manganese. This digest summarizes the annulation reactions via chelation-assisted C−H activation leading to isoquinolines, isoquinolinium salts, or isoquinoline N-oxides. Graphical abstract image
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A concise approach to CF3-containing furan-3-ones, (bis)pyrazoles from novel fluorinated building blocks based on 2,3-butanedione ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Denis N. Bazhin , Dmitry L. Chizhov , Gerd-Volker Röschenthaler , Yulia S. Kudyakova , Yanina V. Burgart , Pavel A. Slepukhin , Victor I. Saloutin , Valery N. Charushin 1,1,1-Trifluoro-4,5,5-trimethoxyhex-3-en-2-one and lithium (2Z)-1,1,1-trifluoro-5,5-dialkoxy-4-oxohex-2-en-2-olate were synthesized for the first time via direct trifluoroacetylation of 2,3-butanedione acetal derivatives. A simple and effective approach to acetal or acyl substituted CF3-pyrazoles, 5,5′-bis(trifluoromethyl)-3,3′-bipyrazole, and, to 5-trifluoromethylfuran-3-ones is presented. Graphical abstract image
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Direct metal-free O-arylation of Biginelli 4-aryl-6-methyl-pyrimidine-2(1H)-one derivatives using diaryliodonium salts ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Prerana B. Thorat , Nitin A. Waghmode , Nandkishor N. Karade 4-Aryl-6-methyl-pyrimidine-2(1H)-one scaffolds of Biginelli type were subjected to C–O cross-coupling reactions using symmetrical diaryliodonium salts under transition metal-free conditions to afford 2-aryloxy pyrimidine derivatives in good to excellent yields. Graphical abstract image
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Syntheses of β- and γ-fluorophenyl cis- and trans-α-methylene-γ-butyrolactones ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): P. Veeraraghavan Ramachandran , Hari Narayanan G. Nair , Pravin Gagare Preparation of a series of cis-γ-fluorophenyl-β-phenyl-α-methylene-γ-butyrolactones is reported via ‘allylboration’ of fluorobenzaldehydes with (E)-methyl 3-phenyl-2-((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)methyl)acrylate. The corresponding trans-γ-fluorophenyl lactones were prepared either (i) via ‘allylboration’ using the (Z)-reagents or (ii) via an indium triflate-mediated isomerization of the cis-products. The difficulty in isomerizing difluorinated cis-products confirms the probable intermediacy of carbocations. Finally, the synthesis of cis-β-fluorophenyl-γ-phenyl-α-methylene-γ-butyrolactones was achieved via an indium-catalyzed allylation–lactonization of aldehydes with (Z)-2-(bromomethyl)-3-(fluorophenyl)acrylates. Graphical abstract image
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The improvement of π-conjugation by the lateral benzene of anthracene and naphthalene ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Jinn-Hsuan Ho , Yu-Hsien Chen , Li-Ting Chou , Po-Wei Lai , Pin-Sian Chen The 1,4-diarylnaphthalenes, 1,4-diarylanthracenes, and 9,10-diarylanthracenes containing the different side arenes, including phenyl, 2-thienyl, and 2-furyl groups, were synthesized to study the influence of structures on π-conjugation. According to photophysics and computation, the smaller dihedral angles and the lateral benzene of anthracene would increase the π-conjugation in some cases. Compared to 1,4-diarylnaphthalenes, 1,4-di(thien-2-yl)anthracene, 1,4-di(fur-2-yl)anthracene, and 9,10-di(fur-2-yl)anthracene displayed better π-conjugation in both of the ground and fluorescing excited states, but 9,10-di(thien-2-yl)anthracene only showed better π-conjugation in the fluorescing excited state. Graphical abstract image
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An expeditious and atom-economic synthesis of lead-like, medicinally important 4,5-dihydropyrazolo[1,5-a]pyrazin-6-ones ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Prashant Mujumdar , Alexander Sapegin , Mikhail Dorogov , Mikhail Krasavin We have developed an expeditious and atom-economic synthesis of lead-like, privileged 4,5-dihydropyrazolo[1,5-a]pyrazin-6-ones, which is based on Sonogashira coupling and a two-step condensation with hydrazine hydrate leading to two ring-forming events, with full control over the two elements of diversity present. Graphical abstract image
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Preparation and diastereo- and enantioselective trifluorocrotylboration with (Z)-(B)-diisopinocampheyl(4,4,4-trifluorobut-2-en-1-yl)borane ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Guisheng Li , Pravin D. Gagare , P. Veeraraghavan Ramachandran Contrary to the non-fluorinated analogs, the hydroboration of trifluoromethylallene with diisopinocampheylborane provides the corresponding Z-trifluorocrotylborane reagent. Trifluorocrotylboration of a series of aldehydes with this reagent provides the corresponding syn-β-trifluoromethyl homoallyl alcohols in high diastereo- and enantioselectivities. Graphical abstract image
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Rapid synthesis of aryl sulfides through metal-free C–S coupling of thioalcohols with diaryliodonium salts ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Dawei Wang , Xin Yu , Keyan Zhao , Liang Li , Yuqiang Ding An efficient, general, and highly selective method for the synthesis of aryl sulfides has been developed through metal-free, direct C–S coupling from thioalcohols and diaryliodonium salts. Significantly, the reaction took only 10min to complete and produced high yields at room temperature. Thus, this methodology proves its value as a versatile synthetic choice for a broad range of aryl sulfides, producing good to excellent yields. Graphical abstract image
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Phosphonium salt induced stereoselective allylic rearrangement during chlorination of α-hydroxyallylphosphinates ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Si-Yu Ji , Yong-Ming Sun , He Zhang , Qing-Gao Hou , Chang-Qiu Zhao α-Hydroxyallylphosphinates were stereoselectively converted to γ-chloro allylphosphinates when treated with Ph3P and CCl4, via substitution of hydroxyl and migration of double bond. The reaction was promoted by phosphonium cation that acted as Lewis acid. Graphical abstract image
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A shortened, protecting group free, synthesis of the anti-wrinkle venom analogue Syn-Ake® exploiting an optimized Hofmann-type rearrangement ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): A.N. Balaev , K.A. Okhmanovich , V.N. Osipov An unusual five-step synthesis of H-β-Ala-Pro-DabNHBz diacetate (a muscular nicotinic acetylcholine receptor antagonist) has been delineated through Hofmann-type rearrangement as a final step to build the target skeleton. The synthesis has been carried out using a protecting group free strategy and employed readily available reagents as the starting materials. Graphical abstract image
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Sodium borohydride mediated reduction of N-Boc protected purines and applications in the synthesis of 7-alkyladenines and tetrahydro[1,4]diazepino-[1,2,3-gh]purines ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Thomas Ihle Aarhus , Urs Fabian Fritze , Martin Hennum , Lise-Lotte Gundersen Electron deficient purines can be reduced to 7,8-dihydropurines when treated with cheap and easy-to-handle sodium borohydride in methanol. The dihydropurine formed by reduction of tris-Boc-protected adenine is a useful intermediate in efficient syntheses of 7-alkyladenines and tetrahydro[1,4]diazepino[1,2,3-gh]purines. Graphical abstract image
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A novel and efficient catalytic system including TEMPO/acetaldoxime/InCl3 for aerobic oxidation of primary amines to oximes ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Jiatao Yu , Xiaohua Cao , Ming Lu A simple and efficient catalytic system including TEMPO/acetaldoxime/InCl3 for aerobic oxidation of primary amines to corresponding oximes by using toluene as the solvent is described. This practical method can use O2 as the economic and green oxidant, tolerate a wide range of substrates, which can afford the target oximes in moderate to excellent yields. Graphical abstract image
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Stereoselective synthesis of cryptomoscatone D2 ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Atla Raju , Gowravaram Sabitha Cryptomoscatone D2 was synthesized stereoselectively from trans-cinnamaldehyde. The synthesis of the triol frame work relied on the creations of the stereocenters independently by utilizing double Maruoka allylations and Sharpless epoxidation. The lactone moiety was constructed by RCM reaction. Graphical abstract image
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[RuCl2(p-cymene)2]2 catalyzed cross dehydrogenative coupling (CDC) toward xanthone and fluorenone analogs through intramolecular C–H bond functionalization reaction ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Sudipta Kumar Manna , Srinivas Lavanya Kumar Manda , Gautam Panda A synthetic approach toward xanthone and fluorenone derivatives through ruthenium catalyzed intra-molecular C–H bond functionalization using an external oxidant has been developed. In the presence of [RuCl2(p-cymene)2]2, a variety of substituted ortho-aryloxy/aryl benzaldehydes underwent cross dehydrogenative coupling to afford the corresponding analogs in moderate to good yields. Graphical abstract image
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Pd-catalyzed atom-economic couplings of triarylbismuth reagents with 2-bromo- and 2,6-dibromochromones and synthesis of medicinally important fisetin ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Maddali L.N. Rao , Abhijeet Kumar Pd-catalyzed mono- and bis-arylation of chromones was demonstrated using triarylbismuths as threefold aryl transfer atom-economic reagents. This unprecedented study involving functionalized chromones afforded regio-selective mono-arylations leading to functionalized 2-arylchromones in good to high yields. Bis-arylation of 2,6-dibromochromones in one-pot operation furnished 2,6-diarylchromones in moderate to good yields. The present methodology was applied in the synthesis of naturally occurring and medicinally important fisetin molecule in high yield. Graphical abstract image
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Amycomycins C and D, new angucyclines from Kitasatospora sp. ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Elke Brötz , Oksana Bilyk , Stephanie Kröger , Thomas Paululat , Andreas Bechthold , Andriy Luzhetskyy Two new angucycline compounds containing O-glycosylated 6-deoxy-α-l-talose were isolated from Kitasatospora sp. The compounds were elucidated based on spectroscopic methods including UV, HR-ESIMS, and NMR. A feeding experiment using alizarin led to the conversion of alizarin to a monoglycosylated product with high efficiency, which allows isolation of the sugar after hydrolysis and determination of the absolute configuration of the sugar. Graphical abstract image
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Acceleration of CuI-catalyzed coupling reaction of alkyl halides with aryl Grignard reagents using lithium chloride ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Kenya Nakata , Chao Feng , Toshifumi Tojo , Yuichi Kobayashi In the presence of LiCl, CuI-catalyzed coupling reaction of R(alkyl)-X with Ar(aryl)MgBr at rt was completed within 2h. Effective leaving groups X in R-X were Br, I, OTs, but not Cl. Grignard reagents ArMgBr with both standard and bulky Ar such as 2-MeC6H4, 2-MeOC6H4, and 2,6-(Me)2C6H3 afforded the desired products in good yields. Ester and cyano groups in R-X were tolerated. Coupling reaction with R(alkyl)-MgBr proceeded as well. Graphical abstract image
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Laboratory and practical synthesis of Suvorexant, a selective dual orexin receptor antagonist ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Daisuke Minehira , Satoyuki Takahara , Isao Adachi , Naoki Toyooka The development of a laboratory and practical synthesis of Suvorexant 1, using intramolecular Mitsunobu cyclization reaction of intermediate 5 as the key reaction, has been reported. Compound 5 was obtained from known chiral ester 2 in three steps, and the key cyclization proceeded smoothly to provide the core seven-membered ring compound 6, which was transformed into 1 by an additional four-step sequence. The procedure described here needs no chiral-HPLC separation, no classical resolution, and no unique enzyme reactions, and offers an alternative practical synthesis of 1. Graphical abstract image
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Design and synthesis of oxa-bowls via Diels–Alder reaction and ring-rearrangement metathesis as key steps ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Sambasivarao Kotha , Ongolu Ravikumar Ring-rearrangement metathesis of norbornene derivatives prepared by Diels–Alder reaction has been used to design various oxa-bowls. Enyne ring-rearrangement metathesis of norbornene ring systems with propargyl moiety produced diene containing oxa-bowls, suitable for further expansion by Diels–Alder strategy. Graphical abstract image
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One-pot synthesis of symmetrical dinucleoside polyphosphates and analogs via 4,5-dicyanoimidazole-promoted tandem P–O coupling reactions ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Qi Sun , Jian Sun , Shan-Shan Gong , Cheng-Jun Wang , Xing-Cong Wang A novel one-pot protocol for the synthesis of symmetrical dinucleoside tri-, tetra-, and pentaphosphates, and their phosphonate analogs simply from nucleoside 5′-phosphoropiperidates has been developed by utilizing 4,5-dicyanoimidazole-promoted tandem P–O coupling reactions. Graphical abstract image
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Channel-dependent conformations of single-strand polymers in organic networks composed of tetrapodal adamantanes with N-heterocyclic moieties ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Masahide Tominaga , Akitaka Iekushi , Kosuke Katagiri , Kazuaki Ohara , Kentaro Yamaguchi , Isao Azumaya Three tetrapodal adamantanes bearing imidazole (1), benzimidazole (2), and phenylimidazole (3) moieties were designed and synthesized. The co-crystallization of polyethylene glycol (PEG) and tetrapodal molecules provided polymer-inclusion organic crystals (1a–3a). Single crystal X-ray analysis revealed that organic networks possessing various channels were produced by CH/N and CH/π interactions. The PEG chain had zigzag, kink-type, and helical conformations. Graphical abstract image
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Solid-phase synthesis of benzazoles, quinazolines, and quinazolinones using an alkoxyamine linker ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Kota Yamaguchi , Takeshi Noda , Yusuke Higuchi , Naoyuki Aoki , Rika Yamaguchi , Miwa Kubo , Kenichi Harada , Yoshiyasu Fukuyama , Hideaki Hioki An alkoxyamine linker was applied for the solid-phase synthesis of benzazoles, quinazolines, and quinazolinones. Aromatic aldehydes were anchored by aldoxime linkage. After some reactions on a solid support, the products were cleaved with paraformaldehyde under the acidic conditions to afford the corresponding aldehydes, which were subsequently subjected to oxidative coupling with 2-substituted anilines under air atmosphere to give the desired compounds. Graphical abstract image
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A short synthesis of the endogenous plant metabolite 7-hydroxyoxindole-3-acetic acid (7-OH-OxIAA) using simultaneous C–H borylations ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Joshua A. Homer , Jonathan Sperry Methyl indole-3-acetate undergoes two simultaneous iridium-catalysed borylations to deliver exclusively 2,7-diboronate, with the ligand 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4Phen) pivotal in driving the diborylation to completion. Subsequent oxidation-hydrolysis of the diboronate provides methyl 7-hydroxyoxindole-3-acetate which upon hydrolysis of the ester delivers 7-OH-OxIAA, an antioxidant, endogenous metabolite of indole-3-acetic acid found in various types of corn. This route has an overall yield of 50%, involves a single chromatographic purification and is an efficient alternative to existing syntheses, made possible by executing simultaneous oxidations at the indole C2 and C7 sites. Graphical abstract image
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Preparation of 5-chloropyrazoles via tandem Meyer–Schuster/von Auwers rearrangements ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Raphaël Dumeunier , Simon Jaeckh , Rebekka Goebel A new, practical preparation of β,β-dichloroenones in three to four steps allows for a straightforward synthesis of 5-chloropyrazoles. Addition of various propargyl anions to commercially available 4-methyl-4-(trichloromethyl)cyclohexa-2,5-dien-1-one gives high yields of the corresponding propargyl alcohols. These are then transformed, in a single step, via two consecutive rearrangements, a Meyer–Schuster and a (sometimes spontaneous) von Auwers rearomatizing rearrangement, to deliver α,α-aryl-trichloromethylketones. After elimination of HCl, cyclization of the β,β-dichloroenones with various hydrazines delivers 5-chloropyrazoles. The four to five step sequence to 5-chloropyrazoles is very atom economical, expelling only water and two molecules of HCl from all the building blocks. Graphical abstract image
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Microwave-assisted chemoselective synthesis of novel pyrazolo[3,4-b]thieno[3,4-e]pyridines: substitution induced axial chirality ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Mani Anusha Rani , Veerappan Jeyachandran , Muthumani Muthu , Subbiah Sivakolunthu , Raju Ranjith Kumar A microwave-assisted chemoselective synthesis of novel pyrazolo[3,4-b]thieno[3,4-e]pyridines has been achieved via tandem Michael addition–cyclization–tautomerization–oxidative aromatization sequence of reactions. Compounds with ortho-substituted phenyl rings exhibited axial chirality due to restricted rotation around C–C single bond. Graphical abstract image
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An efficient protocol for the synthesis of benzoheterocyclic compounds via solid-state melt reaction (SSMR) ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Manickam Bakthadoss , Raman Selvakumar , Jayakumar Srinivasan An efficient protocol for the synthesis of biologically active benzoheterocyclic compounds such as benzothiazoles, benzimidazoles, benzospirothiazoles, and quinoxaline scaffolds have been accomplished via solid state melt reaction (SSMR) with excellent yields. The new protocol does not require any catalyst, solvent, and workup. Two anti-tumor agents have been prepared to demonstrate the application of this new method. Graphical abstract image
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Y(OTf)3 as a highly efficient catalyst in Ferrier Rearrangement for the synthesis of O- and S-2,3-unsaturated glycopyranosides ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Peiran Chen , Shan Li By using Y(OTf)3 as the catalyst, a series of 2,3-unsaturated-glucosides have been synthesized from 3,4,6-tri-O-acetyl-d-glucal, 3,4-di-O-acetyl-l-rhamnal, and 3,4,6-tri-O-benzyl-d-glucal under mild reaction conditions in good yields with high anomeric selectivities. It was found that, in this reaction, 3,4,6-tri-O-benzyl-d-glucal behaved differently from the other two glucals when it was reacted with phenol, O-benzyl glucoside instead of O-phenyl glucoside formed as the sole product. An explanation is given for this phenomenon. Graphical abstract image
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Indirect electrochemical oxidation of substituted polycyclic aromatic hydrocarbons to corresponding para-quinones with potassium bromide in water–chloroform medium ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Palani Natarajan , Vinuta Devi Vagicherla , Muthana Thevar Vijayan Indirect electrochemical synthesis of quinone derivatives of a series of substituted anthracene and naphthalene by the electrolysis of aqueous solution of potassium bromide (3.0M) using Pt anode at constant current density (40mA/cm2) has been carried out. These reactions resulted in good to excellent yields of the corresponding para-quinones as confirmed by physical and spectral data. Graphical abstract image
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Synthesis of enantiopure furo[2,3-b]pyrroles ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Divya S. Nair , Ibrahim Ibnusaud A simple method for the preparation of enantiopure furo[2,3-b]pyrroles, a rare class of concave bicyclic nitrogen and oxygen heterocycle, in promising yield has been developed. The 3-substituted pyrrolidinediones prepared from (2S,3S)-tetrahydro-3-hydroxy-5-oxo-2,3-furandicarboxylic acid (Garcinia acid) have been cyclized diastereo as well as enantioselectively to furo[2,3-b]pyrroles. The cyclization follows Baldwin’s rule. Graphical abstract image
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Two bis(p-phenylene)-34-crown-10-based cryptand constitutional isomers: different binding abilities induced by structural alterations ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Peifa Wei , Zhengtao Li , Binyuan Xia Two novel bis(p-phenylene)-34-crown-10-based cryptand constitutional isomers were prepared and their host–guest complexations with paraquat were studied by ESI-MS, UV–vis spectroscopy, 1H NMR spectra, and X-ray crystal structures. Notably, though the only difference between the two hosts is the location of the nitrogen atom on the third arms, they exhibited quite different binding abilities with paraquat. Competitive complexation was carried out and it may provide a simple way to construct sophisticated supramolecular materials with reversibility and adaptability. Graphical abstract image
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Nucleophilic addition of TMSCCl3 to N-phosphinoyl benzaldimines: a route to N-phosphinoyl-α-(trichloromethyl)benzylamines ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Benoit Wahl , Albert Cabré , Simon Woodward , William Lewis Nucleophilic addition of readily available TMSCCl3 to N-phosphinoyl benzaldimines allows preparation of N-phosphinoyl-α-(trichloromethyl)benzylamines. Typically, the reaction in THF at room temperature using tetrabutylammonium difluorotriphenylsilicate (TBAT) as a catalytic promoter, afforded very good yields (65–95% range) for most derivatives within 1h at room temperature. Graphical abstract image
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New chiral 1,2-aminoalcohols derived from biomass and their application in diethyl zinc additions ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): María M. Zanardi , María C. Botta , Alejandra G. Suárez A convenient procedure for the preparation of chiral 1,2-aminoalcohols starting from levoglucosenone, a biomass derivative, is described. The 1,2-aminoalcohols, bearing primary, secondary, and tertiary amino groups, were tested as chiral catalysts in the asymmetric addition of diethyl zinc to benzaldehyde. Graphical abstract image
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A room temperature discotic mesogenic dyad based-on triphenylene and pentaalkynylbenzene ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Monika Gupta , Indu Bala , Santanu Kumar Pal A facile synthesis of a novel room temperature discotic mesogenic dyad based on triphenylene and pentaalkynylbenzene linked via flexible alkyl spacer is reported. The thermotropic liquid crystalline (LC) property of the compound was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD). The LC property of the dyad was further manipulated by preparing charge transfer (CT) complexes with trinitrofluorenone (TNF). The compound self-assembles into a columnar hexagonal mesophase and exhibits an excellent fluorescent emission property which has possible potential for various opto-electronic applications. Graphical abstract image
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Synthesis and characterization of hydrophilic theophylline base compounds and their use as ligands in the microwave assisted Suzuki–Miyaura couplings of halopyridines in water ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Patricia Conelly-Espinosa , Ruben A. Toscano , David Morales-Morales Xanthine derivatives, caffeine (L1), theobromine (L2), theophylline (L3), 7-(β-hydroxyethyltheophylline) (L4), (7-(2,3-dihydroxypropyl)theophylline) (L5), and theophylline 7-acetic acid (L6) and the acetylated derivatives of the later three (L7–L9) were employed as ligands for the in situ palladium catalyzed Suzuki–Miyaura cross couplings of a series of halogenated pyridines. Optimized conditions were found where the diacetylated ligand (L8) was determined to be the best for this process, producing good to excellent yields in the couplings of halogenated anilines with phenylboronic acid under mild reaction conditions in water using microwave irradiation. Graphical abstract image
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Aldol reaction of kojic acid using alumina supported base catalyst and enzymatic resolution of the aldol adduct by CALB ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Deepak K. Sharma , Baldev Singh , Debaraj Mukherjee An efficient and ecofriendly aldol reaction of kojic acid with aldehydes using a heterogeneous reusable catalyst (alumina modified with base) is developed. Enzymatic hydrolytic resolution of the racemic acetylated aldol adduct 2 was achieved using lipase from Candida antarctica type B (CALB). The key feature of this enzymatic resolution is that regioselective deacetylation of ester derived from the primary alcohol located away from the stereocentre occurred in the presence of adjacent secondary acetate. Graphical abstract image
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Novel α-tosyloxylation of ketones catalyzed by the in situ generated hypoiodous acid from alkyl iodide ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Bijun Zhang , Liuquan Han , Jiantao Hu , Jie Yan Using a catalytic amount of 1-iodopropane, a novel and efficient procedure has been developed for direct preparation of α-tosyloxyketones from ketones. In this protocol, 1-iodopropane is first oxidized into iodosylpropane, which decomposes to form the key catalyst hypoiodous acid. With this method, not only α-tosyloxyketones, but also other α-sulfonyloxyketones have been prepared in moderate to good yields, which extends the application of alkyl substituted hypervalent iodine reagents in organic synthesis. Graphical abstract image
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A green bromination process for synthesis of a novel drug candidate ()
Publication date: 15 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 42 Author(s): Steven R. Mathieu , George A. Moniz A bromination process has been developed using a salt-based brominating reagent and a non-chlorinated solvent system. The process affords enhanced selectivity and enables product isolation by simple filtration of the reaction mixture, resulting in a substantially reduced waste stream. Graphical abstract image
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Editorial board ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41
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Graphical Contents List ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41
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N-alkylation of lactams with secondary heterobenzylic bromides ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Ming Yu , Karis Stevenson , Gene Zhou We herein report a general N-alkylation reaction of lactams with secondary heterobenzylic bromides. This methodology features mild reaction condition, moderate to high product isolation yield, and broad substrate scope. Good chemical and structural tolerance has also been demonstrated by both the secondary heterobenzylic bromides and lactam substrates. Graphical abstract image
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Synthesis of N-alkyl-N′-aryl-piperazines via copper-catalyzed C–N bond formation ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Issa Yavari , Mohammad J. Bayat , Majid Ghazanfarpour-Darjani An efficient copper-catalyzed tandem synthesis of N-alkyl-N′-aryl-piperazines from 1,4-diaza-bicyclo[2.2.2]octane, alkyl halides, and aryl halides in the presence of copper(I) iodide and potassium tert-butoxide in DMSO is described. Graphical abstract image
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An efficient solvent-tuning approach for the rapid synthesis of thiazolidinone derivatives and the selective synthesis of 2-amino-4H-1,3-thiazin-4-one and dimethyl 3,3′-thiodiacrylates ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Garima Choudhary , Rama Krishna Peddinti Green synthetic approach has been developed for the rapid generation of thiazolidinone derivatives as crystallized products under catalyst-free conditions in water by polarity adjustment with ethyl lactate as a co-solvent in excellent yields. Additionally, interesting findings on the selective synthesis of 2-amino-4H-1,3-thiazin-4-one and dimethyl 3,3′-thiodiacrylates have been reported. Graphical abstract image
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Chromeno[2,3-c]pyrroles by one-pot multicomponent domino addition–amination reaction ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Michael A. Terzidis , Vassilios G. Tsiaras , Nicolaos M. Drosos , Paraskevi M. Kasapidou , Julia Stephanidou-Stephanatou , Constantinos A. Tsoleridis , Gernot Buth , George E. Kostakis A new aspect concerning chromone chemistry leading to the one-pot synthesis of chromeno[2,3-c]pyrroles is described. The synthesis involves a multicomponent reaction of 3-formylchromones with isocyanides and azodicarboxylates, whereupon novel chromeno[2,3-c]pyrrole derivatives were formed in good yields. The structures of the products were elucidated by 1D and 2D NMR experiments and were unambiguously confirmed by the use of crystal X-ray diffraction analysis. Full assignment of all 1H and 13C NMR chemical shifts has been achieved. A plausible mechanistic scheme is proposed. Graphical abstract image
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Phosphorus deprotonation by a non-nucleophilic base is critical for the synthesis of nucleoside α-P-boranodiphosphates via a phosphoramidite approach ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Zhihong Xu , Barbara Ramsay Shaw Here we report the synthesis of nucleoside α-P-boranodiphosphate analogs via our improved phosphoramidite approach, where the addition of a non-nucleophilic base, TEA, to deprotonate phosphorus is considered to be critical to improve final product yields. Protonation on trivalent phosphorus might not only have blocked Lewis acid borane modification, but also have promoted byproduct formation through a trans-nucleophile process. Here, based on 31P NMR data, mechanisms are proposed for P(V)P(III) bond cleavage via phosphorus protonation-promoted nucleophile-exchange, and TEA deprotonation of phosphorus in promoting product formation in anhydrous synthetic reaction mixtures. Graphical abstract image
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A facile route for the synthesis of novel S-linked 1,3,5-triazine tethered peptidomimetics ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Muniyappa Krishnamurthy , Basavaprabhu , K.M. Sharanabai , Vommina V. Sureshbabu An efficient one-pot synthesis of Nα-protected S-linked 1,3,5-triazine tethered peptidomimetics is described. The protocol involves a three-component condensation reaction employing Nα-protected amino alkyl isothiouronium salt, formaldehyde and amino acid ester or aryl amine as reactants. Various aryl amines with substitutions and amino acids with simple as well as bifunctional side chains were employed to obtain triazine tethered peptidomimetics in good yield. Graphical abstract image
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Hydrated ferric sulfate catalyzed synthesis of 5,6-unsubstituted 1,4-dihydropyridines using three-component reaction ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Kobirul Islam , Deb K. Das , Abu T. Khan A wide variety of 5,6-unsubstituted 1,4-dihydropyridines derivatives (4a–q) were synthesized through a one-pot three-component reaction from α,β-unsaturated aldehydes, amines, and 1,3-diketones at room temperature using hydrated ferric sulfate as a Lewis acid catalyst. The key features of the present protocol are mild and simple reaction procedure, good to excellent yields, and use of inexpensive, recyclable, and environmentally benign catalyst. Graphical abstract image
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I2-mediated C3-formylation of indoles by tertiary amine and H2O ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Bo Zhang , Bin Liu , Jianbin Chen , Jiehui Wang , Miaochang Liu An I2-promoted 3-formylation of free (N–H) and N-substituted indoles with tetramethylethylenediamine (TMEDA) and H2O as the carbonyl source is achieved, providing 3-formylindole in moderate to excellent yields with good functional group tolerance. This procedure represents an exceedingly attractive alternative to the traditional formylation methods. Graphical abstract image
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A new approach to the synthesis of cross-conjugated cyclopentenone prostaglandins. Synthesis of (±)-15-deoxy-Δ12,14-prostaglandin J2 methyl ester ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): N.S. Vostrikov , I.F. Lobko , M.S. Miftakhov A new approach to 15-deoxy-Δ12,14-prostaglandin J2 and related structures based on the (±)-Corey lactone diol has been developed. The key stage of this approach involves building the structure of a prostaglandin (PG) derivative with leaving groups at positions 9, 13, and 15, followed by elimination of these groups by treatment with an organic base. Graphical abstract image
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