Diels-Alder reactions of acyclic α-cyano α,β-alkenones: a new approach to highly substituted cyclohexene system

The Diels-Alder reactions of a variety of acyclic α-cyano α,β-unsaturated ketones 8 have been investigated. With the assistance of boron trichloride, these compounds were found to undergo the cycloaddition readily with dienes to give the corresponding adducts 9 in good to high yields. In addition, some of 9 could be further subjected to the reductive alkylation reactions using lithium naphthalenide (LN) and an appropriate alkylating agent, thus allowing for the generation of highly substituted cyclohexenes 10 with the replacement of the cyano group with an alkyl substituent.