Sodium cyanoborohydride → 1,2-Dibromo-4,4-dimethylcyclopentene

Participants

Reaction Steps

Under nitrogen, a stirred solution of 3.7 g (7.3 mmol) of 1,2-dibromo-4,4-di(iodomethyl)cyclopentene (Step 7) and 1.3 g (20.6 mmol) of sodium cyanoborohydride in 15 mL of hexamethylphosphoramide (HMPA) was heated to 100° C. in an oil bath overnight. The reaction was cooled, diluted with 50 mL of water, and extracted 5 times with ethyl acetate/hexane (1:5). The combined extracts were washed 3 times with water, dried (Na2SO4), and concentrated in vacuo. Purification by silica gel chromatography (Waters Prep-500) with hexane gave 1.3 g (70%) of 1,2-dibromo-4,4-dimethylcyclopentene (16 in Synthetic Scheme V) as a colorless oil: NMR (CDCl3) d 1.16 (s, 6H), 2.44 (s, 4H); MS (EI)m/e (rel intensity) 256 (24), 254 (63), 252(44), 175 (26), 173 (29), 94 (100).

Provenance & Evidence