Aspectos regio- e estereoquímicos da adição de Michael assimétrica via iminas quirais com centros estereogênicos pré-existentes/ Regio- and stereochemical aspects of the asymmetric Michael addition using chiral imines bearing a resident stereogenic center
Resumo em inglês The asymmetric Michael addition reactions using chiral imines, under neutral conditions (deracemizing alkylation process), constitute one of the main methods for the stereocontrolled elaboration of quaternary carbon centers. This protocol is based on the conjugate addition of secondary chiral enamines to electron-deficient alkenes. The focus of this report deals with the discussion of regio- and stereochemical aspects of the deracemizing alkylation process concerning enamines bearing a resident chiral center.
Estudo experimental e teórico da redução de bases de Schiff derivadas da 3,3-difenilpropilamina/ Experimental and theoretical study of the reduction of Schiff bases derivated from 3,3-diphenylpropilamine
Resumo em inglês A series of seven Schiff bases have been synthesized from 3,3-diphenylpropilamine and substituted benzaldehydes. These imines were treated with NaBH4 in ethanol affording the corresponding amines in 98-55% yields. A molecular modeling study was performed with the Schiff bases in order to compare the theoretical parameters with the experimental results. The theoretical parameters were obtained by AM1 and PM3 semi-empirical methods. The analysis of charge, electron densitie (mais) s and LUMO coefficients suggested that the most favorable interactions should occur with Schiff bases containing electron-donating groups, in accordance with experimental yields, showing that the higher reactivity is due to higher electrophilic character of imine carbons.