N-Tetrahydropyranyl or N-THP

Protection

6-Bromo-4-methyl-1H-indazole (1.0g, 4.7 mmol) and p-TSA (0.082 g, 0.47 mmol) were dissolved in THF (20 mL). 3,4-Dihydro-2H-pyran (1.99 g, 23.7 mmol) was addes and the mixture was heated at about 70°C for about 6 hours. The mixture was concentrated in vacuo and the residue was purified by silica gel chromatography (5:1 hexanes:AcOEt) to give THP protective compound (0.8 g, 41%). 

Patent reference: WO2012048222 (Abbott)

Deprotection

A flask was charged with THP protective compound (0.19 g, 0.45 mmol) and 4M HCl in 1,4-dioxane (2 mL). The mixture was stirred at about 50°C for about 2h, cooled to rt, concentrated under reduced pressure and purified by reverse phase HPLC to give deprotective compound (0.03 g, 20%). 

Patent reference: WO2012048222 (Abbott)

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