Patent ID: 6479672
Filing Date: 2002-11-12
Classification: C07D

Abstract:
A diastereoselective method for preparing a Michael adduct of formula (III) whereinn is 1, 2 or 3; R1 is an optionally substituted hydrocarbyl group; and Ra is a bulky group selected from t-butyl, phenyl, diphenylmethyl, trityl, trichloromethyl and mesityl; which comprises (a) contacting a chiral 2,5-disubstituted- 1,3-dioxolan-4-one of formula (I) â€ƒwith a base capable of generating an enolate of said dioxolanone to provide the corresponding enolate; (b) contacting said enolate with a zinc-amine complex followed by addition of the free amine, wherein the amine of the zinc-amine complex and the free amine are the same and are of formula (IV) whereinL is C2-6 alkylene or C2-6 alkenyl each of which may be optionally interrupted by a heteroatom selected from O, S and Nâ€”Rc wherein Rc is H or C1-6 alkyl; Rb is independently H or C1-4 alkyl; or 2 Rbs together with the N to which they are attached form a 5- or 6-membered ring optionally containing an additional heteroatom selected from O, S and Nâ€”Rc wherein Rc is H or C1-6alkyl; and (c) contacting the mixture of step (b) with a cycloalkenone of formula (II) to provide the Michael adduct of formula (III).