C. Lopez-Mardomingo

Stereochemistry of imino-group reduction. Part 3. The hydride reduction of achiral benzil monoimines

The RR,SS:RS,SR ratio of diastereoisomeric amino-alcohols obtained from the lithium aluminium hydride reduction of the monoimines prepared by reaction of benzil and various aliphatic and aromatic achiral amines has been determined. Stereochemical results are analysed in terms of competition between two reaction routes involving respectively preliminary reduction of the oxo group and the imino group. The influence of polar and steric factors of the nitrogen substituent is discussed as is also that of solvent polarity. The reduction of some monoimines with sodium borohydride has also been studied. An interpretation of the ratios RR,SS:RS,SR is provided.

Stereochemistry of imino-group reduction. Part 6. Stereochemistry of reduction of 1,2-imino ketones having a pre-existing chiral centre. Synthesis of amino alcohols with three chiral centres

Stereochemical results of the lithium aluminium hydride and sodium borohydride reduction of 1,2-imino ketones, PhCOCPhNCHRPh (R = Me, Et, Pr, Bu, Bui, Pri, But), are reported. The stereoselectivity is accounted for by competition between two possible reactions: that proceeding through previous reduction of the carbonyl group and that involving previous reduction of the imino group. The relative involvement of both reaction routes depends upon the nature of the reagent and the relative hard–soft character of both functional groups in the imino ketones. The influence of steric effects of the R groups is discussed.

The stereoselective reduction of α-aminodeoxybenzoin derivatives with sodium borohydride

Abstract Total stereoselectivity is observed in the sodium borohydride reduction of α-aminodeoxybenzoins and their hydrochlorides in various hydroxylic solvents. RS - SR isomer (erythro) was the only aminoalcohol obtained.

Configurational assignment to N-(1-phenylalkyl)-substituted 2-amino-1,2-diphenylethanols

Three-chiral centre aminoethanols are obtained by reduction of 1,2-imino ketones having a pre-existenting chiral centre. Assignment of configuration to the aminoethanols has been carried out on the basis of high-dilution i.r., 1H n.m.r., and 13C n.m.r. spectroscopic data.