Aromatic Annulation of Alicyclic alpha,beta-Unsaturated Aldehydes: Synthesis of Chirally Substituted Tetrahydronaphthalenes.

Chiral 2-tetrahydronaphthalene-carboxylic acid derivatives 3, 6, and 9 were prepared by functionalization of enantiopure terpenic unsaturated aldehydes 1, 4, 7 with triphenyl-(alpha-carbethoxy-beta-carboxyethyl)-phosphonium betaine, followed by a cyclization reaction promoted by ethyl chloroformate under basic conditions.