Enantioselective synthesis of the fragrance trans-magnolione under asymmetric phase transfer catalysis

Abstract The stereoselective synthesis of the fragrance trans -magnolione ( 1 ) through conjugate Michael addition of alkyl acetoacetates to 2-pentyl-2-cyclopentenone ( 2 ) under solid/liquid phase transfer catalysis (PTC) is reported. Under optimized conditions, the 1,4-addition of tert -butyl acetoacetate to enone 2 catalyzed by N -9-anthracenylmethylquininium chloride ( 4 ) affords, after hydrolysis and decarboxylation, trans -( 2S , 3S )- 1 with 85/15 d.r. and 74% ee. The use of the pseudo -enantiomeric catalyst N -9-anthracenymethylquinidinium chloride ( 5 ) allows obtaining the enantiomer trans -( 2R , 3R )- 1 with comparable enantio- and diastereoselectivity. To cite this article: S. Superchi et al., C. R. Chimie 8 (2005) .