2-Cycloalkenones tandem vicinal difunctionalization

The synthetic implications of this discovery were slow to be exploited. Base-initiated dimerizations of 2-cycloalkenones, known to give crystalline solids,3233 remained puzzling for some time before conjugate additions were suggested to account for some of the possible products 34 indeed, the product of base-catalyzed dimerization of 4,4-dimethyl-2-cyclopentenone, which proceeds via a double Michael addition sequence, was not identified until 1969 (Scheme 2).35 An unanticipated cyclopropanation reaction of acrylaldehyde36 37 using ethyl bromomalonate and proceeding by means of a similar Michael addi-tion-Sw enolate alkylation represents an early synthetic use of tandem vicinal difunctionalization. 

Ketones, specifically 2-alkenones and 2-cycloalkenones, have been used extensively as substrates for tandem vicinal difunctionalization, allowing delineation of various reactivity patterns based upon the structural elements present in the enone. Aldehyde substrates have been used less widely comparison... 

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