PREPARATION OF SILYL ENOL ETHERS BY THE REACTION OF KETONES WITH SILYLAMINES AND METHYL-IODIDE

Transformation of ketones to silyl enol ethers using (trimethylsilyl)d iethylamine and methyliodide is described. Both cyclic and acyclic ket ones gave silyl enol ethers in high yield, whose stereochemistry showe d that the formation of thermodynamically stable isomers was favored. A cyclic diketone, 1,4-cyclohexanedione, gave a 1:1 mixture of 1,4-bis ((trimethylsilyl)oxy)-1,3-cyclohexadiene and 1,4-bis((trimethylsilyl)o xy)-1,3-cyclohediene, while 1,3-cyclohexanedione gave 3-((trimethylsil yl)oxy)-2-cyclohexenone alone. The tert-butyldimethylsilyl enol ethers of ketones also were obtained in high yield when (tert-butyldimethyls ilyl)diethylamine, combined with methyl iodide, was used. A combinatio n of allyl bromide and (trimethylsilyl)diethylamine was also effective for the transformation of ketones to silyl enol ethers.