Tetrahedron: Asymmetry

Enantioselective quaternization of 4-substituted oxazol-5-(4H)-ones using recoverable Cinchona-derived dimeric ammonium salts as phase-transfer organocatalysts

S Tarí, A Avila, R Chinchilla, C Nájera

Index: Tari, Silvia; Avila, Angel; Chinchilla, Rafael; Najera, Carmen Tetrahedron Asymmetry, 2012 , vol. 23, # 2 p. 176 - 180

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Citation Number: 11

Abstract

Dimeric anthracenyldimethyl-derived Cinchona ammonium salts are used as chiral organocatalysts (5mol%) for the enantioselective 4-alkylation of 4-substituted azlactones. The corresponding adducts bearing a new quaternary center were obtained with up to 80% ee when using a dimeric ammonium salt derived from cinchonidine, and are precursors of α, α-disubstituted α-amino acids. The catalysts can be recovered almost quantitatively by ...