The Li carbenoids 4, prepared by treatment of substituted 1, l-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a+, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C (1) ...
![5-[2-(Trimethylsilyl)cycloprop-1-ylidene]cyclopenta-1,3-diene Structure](https://image.chemsrc.com/caspic/282/79209-37-3.png)
