Trimethyl borate → Ammonia

Participants

Reaction Conditions

Reaction Steps

n-Butyl lithium (2.5M in hexanes, 0.18 mL, 0.45 mmol) was added dropwise to a solution of the product of example 87 (200 mg, 0.38 mmol) in tetrahydrofuran (5 mL), cooled to −78° C., and the mixture was stirred for 15 minutes. Trimethylborate (0.13 mL, 1.13 mmol) was added and the mixture was stirred at −78° C. for 30 minutes and at room temperature for 2 hours. 4-methylmorpholine N-oxide (132 mg, 1.13 mmol) was added and the mixture was heated under reflux for 4 hours and stirred at room temperature for 18 hours. The reaction mixture was then partitioned between ethyl acetate (30 mL) and water (30 mL) and the organic layer was separated and washed with water (20 mL). The organic solution was dried over sodium sulfate, concentrated in vacuo and the residue was purified by column chromatography on silica gel, eluting with dichloromethane:methanol:0.88 ammonia, 100:0.0 to 90:10:1. The appropriate fractions were evaporated under reduced pressure and the residue was further purified by preparative tlc, eluting with dichloromethane:methanol:0.88 ammonia, 90:10:1, to afford the title compound as a gum in 3% yield, 5 mg.

Provenance & Evidence