Asymmetric addition of dimethylzinc to malonates: a new synthetic strategy to valuable fragrances

ASYMMETRIC ADDITION OF DIMETHYLZINC TO MALONATES: A NEW SYNTHETIC STRATEGY TO VALUABLE FRAGRANCES P. Scafato, V. Marchitiello, L. Pisani, S. Superchi, C. Rosini Dipartimento di Chimica, Università degli Studi della Basilicata, via N. Sauro, 85; Potenza. e-mail: pisani.laura@virgilio.it The copper-catalyzed conjugate addition of organozinc reagent to α,β-unsaturated carbonyl compounds is a widely used strategy for the catalytic asymmetric C-C bond formation, with a large spectrum of substrates.1 Unfortunately, acyclic esters are not reactive in this reaction, in spite of the remarkable importance of chiral 3-alkylsubstituted esters both in asymmetric synthesis and as precursor of biologically active compounds. Recently, an efficient addition of dimethylzinc to unsaturated malonates, which can easily be transformed in monoesters by dealkoxycarbonylation, has been set up.2 We report herein the asymmetric addition of dimethylzinc to 3-phenylpropyliden malonate as a new route for the preparation of the valuable fragrances,3 Phenoxanol, Citralis and Nitrile Citralis, in optically active form. References: 1) a) Feringa, B.L. Acc. Chem. Res. 2000, 33, 346. b) Alexakis, A.; Benhaim, C. Eur J. Org. Chem, 2002, 3221. 2) Schuppan, J.; Minnaard, A. J.; Feringa, B. L. Chem. Comm. 2004, 792. 3) Matteoli, U.; Ciappa, A.; Bovo,S.; Bertoldini, M.; Scrivanti, A. Tetrahedron:Asymmetry. 2007, 18, 797.