IRON(III) MEDIATED TRANSFORMATIONS OF TRIMETHYLSILYLOXY CYCLOPROPYL ETHERS .2. A NEW 4-SUBSTITUTED-2-CYCLOHEXENONE SYNTHESIS

Conjugate addition of a variety of Grignard reagents to 2-cyclopenteno ne gave a number of silyl enol ethers (1) which were treated with Et(2 )Zn/CH2I2 to give the corresponding cyclopropyl silyl ethers (2) in go od yield. Ferric chloride ring expansion followed by base elimination of the resulting beta-chloro ketones gave the 4-substituted-2-cyclohex enones (4) in moderate to good overall yield. The overall process prov ides a convenient three step route to these enones from 2-cyclopenteno me.