摘要:
A new procedure for cyclohexenone annelation has been developed. Thus, alkylation of 4-isopropylcyclohexanone with allyl bromide gives, over several steps, ketone 8, Exposure to (trimethylsilyl)diazomethane and MeLi smoothly cyclized 8 to the cyclopentene 9 by insertion of the intermediate alkylidene carbene into the unactivated methylene CH. On debenzylation, ozonolysis, and subsequent aldol condensation, 9 is transformed into oxo-T-cadinol(1).