Nitrogen → Methanesulfonic acid 4-(2-methyl-[1,3]dioxolan-2-yl)-pyridin-2-ylmethyl ester

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反応手順

In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), a solution of [4-(2-methyl-[1,3]dioxolan-2-yl)-pyridin-2-yl]-methanol (177 mg, 0.91 mmol) in dry CH2Cl2 (5 mL) was treated at 0° C. with Et3N (0.16 mL, 1.17 mmol) followed by DMAP (11 mg, 0.09 mmol) and Ms-Cl (0.09 mL, 1.14 mmol). After stirring at rt for 2 h, the reaction was quenched with water (5 mL). The org. layer was dried over MgSO4, filtered, and the solvent was removed under reduced pressure to give crude methanesulfonic acid 4-(2-methyl-[1,3]dioxolan-2-yl)-pyridin-2-ylmethyl ester as a red oil. The crude material (246 mg) was dissolved in acetone (12 mL) under inert atmosphere (N2). 4-Nitro-1H-pyrazole (114 mg, 0.90 mmol) was added followed by K2CO3 (628 mg, 4.50 mmol) and TBA bromide (58 mg, 0.18 mmol). The reaction mixture was stirred overnight at rt and concentrated to dryness. The residue was partitioned between water (5 mL) and EA (10 mL). The layers were separated and the aq. layer extracted with EA (2×10 mL). The combined org. extracts were dried over MgSO4, filtered, and the solvent removed under reduced pressure. Purification of the residue by FC (10:1 to 2:1 hept-EA) gave the title compound as a pale yellow solid. TLC: rf (1:1 hept-EA)=0.10. LC-MS-conditions 02: tR=0.85 min, [M+H]+=291.31.

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