Introduction of Electrophiles to the α-Position of α,β-Unsaturated Aldehydes and Ketones by Sequential Conjugate Aminosilylation-Alkylation-Deamination
Silylamines add to α,β-unsaturated aldehydes and ketones in 1,4-addition mode to generate amino-substituted silyl enolethers without any catalysts. These easily isolable silyl enolethers react with acetals and aldehydes in the presence of a Lewisacid to give α-alkoxyalkyl and α-hydroxyalkyl substitutedα,β-unsaturatedcarbonylcompounds, respectively, after deamination by treatment with silica gel
Ene reaction proceeds between 1-alkyl-1,2-propadienyl sulfides and aldehydes in the presence of BF3·OEt2 to afford 1,3-dienes possessing an alkylthio group. On the other hand, the reactions of 1-silyl-1,2-propadienyl sulfides with aldehydes or their dimethylacetals give aldol-type addition products, α-methylene acylsilanes.