Iron(III) mediated transformations of trimethylsilyloxy cyclopropyl ethers. Part 2: A new 4-substituted-2-cyclohexenone synthesis

Article abstract of DOI:10.1016/0040-4020(95)00817-R

Conjugate addition of a variety of Grignard reagents to 2-cyclopentenone gave a number of silyl enol ethers (1) which were treated with Et₂Zn/CH₂I₂ to give the corresponding cyclopropyl silyl ethers (2) in good yield. Ferric chloride ring expansion followed by base elimination of the resulting β-chloro ketones gave the 4-substituted-2-cyclohexenones (4) in moderate to good overall yield. The overall process provides a convenient three step route to these enones from 2-cyclopentenone.