title: Highly diastereoselective arylation of (S)-mandelic acid enolate: enantioselective synthesis of substituted (R)-3-hydroxy-3-phenyloxindoles and (R)-benzylic acids and synthesis of nitrobenzophenones.
abstract: An easy access to substituted (R)-3-hydroxy-3-phenyloxindoles, (R)-benzylic acids, and benzophenones is described. The reaction of the lithium enolate of the (2S,5S)-cis-1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with several o- and p-halonitrobenzenes proceeds readily to give the corresponding arylation products in good yields and diastereoselectivities. The reduction of the nitro group with Zn/HCl/EtOH in the o-nitro arylation products with concomitant intramolecular aminolysis of the dioxolanone moiety leads directly to enantiomerically pure (R)-3-hydroxy-3-phenyloxindoles. On the other hand the basic hydrolysis of the dioxolanone moiety in all the arylation products (ortho and para) leads to enantiomerically pure substituted (R)-benzylic acids. The oxidative decarboxylation of these latter with oxygen as terminal oxidant in the presence of pivalaldehyde and the Co(III)-Me2opba complex as catalyst gives substituted nitrobenzophenones.
authors.affiliation: Departament de Química Orgànica, Facultat de Química, Universitat de València, Dr. Moliner 50, E-46100 Burjassot, València, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Barroso
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Blay
authors.forename: Luz
authors.initials: L
authors.lastname: Cardona
authors.forename: Isabel
authors.initials: I
authors.lastname: Fernández
authors.forename: Begoña
authors.initials: B
authors.lastname: García
authors.forename: José R
authors.initials: JR
authors.lastname: Pedro