Novel DBU-MeOH-Promoted One-Pot Stereoselective γ-Functionalization of 1,3-Dicarbonyls: An Easy Access to γ-Arylidene, γ-Alkylidene and γ-Allylidene α-Ketoesters and -amides

Abstract

Cyclic β-ketoesters and β-ketoamides undergo, in a one-pot process, an unprecedented DBU-MeOH-promoted regio- and stereoselective γ-functionalization with aldehydes, by a directed γ-aldol reaction and dehydration sequence, to afford synthetically valuable alkylidene (or arylidene) cycloalkanones in good yields. While β-ketoesters give good results only with aromatic aldehydes, β-ketoamides react smoothly either with aromatic, aliphatic, or α,β-unsaturated aldehydes following a totally regioselective 1,2-addition. The overall sequence, probably initiated by a reversible α-aldol reaction, allows the formation of hitherto unknown and stereodefined γ-functionalized cycloalkanones having three reactive centers, such as two electrophilic and one nucleophilic site.