Acetic Acid → 2-Methyl-6-nitro-2,3-dihydroimidazo[2,1-b][1,3]oxazole

Participants

Reaction Steps

A mixture of tert-butyl (R)-4-(2-methyl-6-nitro-2,3-dihydroimidazo[2,1-b]oxazol-2-ylmethyl)-piperazine-1-carboxylate prepared in Example 396 (100 mg, 0.27 mmol) and trifluoroacetic acid (2 ml) was stirred at room temperature for 3 hours. The reaction mixture was concentrated under reduced pressure. The residue was dissolved in methylene chloride (5 ml) and neutralized with triethylamine (1 ml, 7.17 mmol), and then the solution was concentrated under reduced pressure. The residue was dissolved in methanol (5 ml). To the solution, 4-phenylbenzaldehyde (149 mg, 0.82 mmol), sodium cyanotrihydroborate (51 mg, 0.82 mmol) and acetic acid (48 μl, 0.82 mmol) were added in this order followed by stirring at room temperature for 15 hours. The reaction mixture was concentrated under reduced pressure, and the residue was added a saturated sodium hydrogencarbonate solution. The precipitates were filtered off and purified by silica gel column chromatography (ethyl acetate) to afford (R)-2-(biphenyl-4-ylmethyl)piperazin-1-ylmethyl)-2-methyl-6-nitro-2,3-dihydroimidazo[2,1-b]oxazole (67 mg, yield 57%) as a light yellow powder.

Provenance & Evidence