p-Toluenesulfonic acid monohydrate → (1R,6S)- 4,7,7-Trimethyl-3-oxabicyclo[4.1.0]hept-4-en-2-one

Participants

Reaction Steps

A solution of 20 g (0.17 mol) of (1R,cis)-2,2-dimethyl-3-(2-oxopropyl)cyclopropane-1-carboxylic acid and 3 g (0.016 mol) of p-toluenesulfonic acid monohydrate in 93 ml of acetic anhydride and 150 ml of benzene was stirred for 30 minutes at 10°-20° C. The slightly darkened mixture was diluted with ether and washed with ice cold saturated sodium bicarbonate solution until the washings were basic. The organic phase was dried over anhydrous magnesium sulfate and decolorized with charcoal. The solvent was evaporated in vacuo to give 24 g (93%) of the product as a tan solid. Recrystallization from pentane gave a white solid mp: 44°-45.5° C., [α]D25 -85.6° (c=2.0; CHCl3).

Provenance & Evidence