The Vinylogous Intramolecular Morita−Baylis−Hillman Reaction: Synthesis of Functionalized Cyclopentenes and Cyclohexenes with Trialkylphosphines as Nucleophilic Catalysts

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Abstract
The development of the vinylogous intramolecular Morita−Baylis−Hillman reaction for the synthesis of functionalized cyclopentenes and cyclohexenes is described. The reaction involves the trialkyphosphine-catalyzed cyclization of 1,6- or 1,7-diactivated 1,5-hexadienes or 1,6-heptadienes, containing carboxyaldehyde, methyl ketone, or methoxycarbonyl as the olefin activating groups. A representative example of this reaction is the Me3P-catalyzed cyclization of 1a in tert-amyl alcohol, which provides the substituted cyclopentene 2a in 95% yield and with 97:3 regioselectivity.