From Simmons-Smith Cyclopropanation of a-Enone Enol Ethers

3 From Simmons-Smith Cyclopropanation of a-Enone Enol Ethers 

The selective cyclopropanation of the a-enone silyl enol ether 75, by methylene iodide and the zinc-silver couple 2), is remarkable. Only the double bond bearing the tri-methylsiloxy group reacted to yield the 1-trimethylsiloxy vinylcyclopropane 76 when not more than 1.1 equivalent of the Simmons-Smith reagent was used, but the bis-cyclopropanation product 77 was obtained in good yield with an excess (3 equivalents) of the cyclopropanating reagent, Eq. (24) 42). 

Subsequent treatment with methanol led to 1-vinyl- and 1-cyclopropylcyclopropa-nols respectively and with IM methanolic sodium hydroxide to the corresponding  

Simmons-Smith regioselective cyclopropanation of a-enone alkyl enol ethers also provided 1-alkoxyvinylcyclopropanes in high yields43 . 

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