Aprotic Conjugate Addition Reactions of Lithiated Allylic Sulfoxides With Acyclic Enones; a Breakdown of the trans-Decalyl Transition State

The reactions of lithiated 1-(t-butylsulfinyl)prop-2-ene, 1-(t-butylsulfinyl)-3-methylbut-2-ene, 1-(t-butylsulfinyl)but-2-ene, 1-(phenylsulfinyl)but-2-ene and 2-methyl-1-(phenylsu1finyl)prop- 2-ene with methyl vinyl ketone, mesityl oxide and crotonaldehyde give largely carbonyl addition products arising from reaction through C1 or C3 of the allyl system. In the case of methyl crotonate, conjugate addition through C3 is observed. The initially formed diastereomers of the C1 adducts, allylic sulfoxides, are configurationally unstable. Only the lithiated 1-(t-butylsulfinyl)-3-methylbut-2-ene undergoes conjugate addition with methyl vinyl ketone to give an (E)-vinyl sulfoxide whose formation may involve the trans-decalyl transition state characteristic of the reactions of lithiated allylic sulfoxides with cyclic enones.