Convergent Catalysis: Asymmetric Synthesis of Dihydroquinolines Using a Combined Metal Catalysis and Organocatalysis Approach

Abstract

A convergent catalysis approach has been developed. The combined metal-catalyzed and organocatalyzed cascade consists of two oxidations, an aza-Michael addition and an aldol condensation, and involves a multicatalysis approach to provide 1,2-dihydroquinolines in a highly enantioselective fashion.

Enantioselective Desymmetrization ofpara-Quinamines through an Aminocatalyzed Aza-Michael/Cyclization Cascade Reaction

“…15 We began our investigation by studying the reaction of the readily available para-quinamine 1a with trans-cinnamaldehyde 2a in the presence of diarylprolinol silyl ether catalysts 3 and AcONa (Table 1). 16 The tosyl nitrogen protecting group of 1a is essential to the success of the reaction. 17 For instance, acetyl or tert-butoxycarbonyl groups shut down the reactivity of the paraquinamines because these groups rendered the NH less acidic for a subsequent deprotonation under basic conditions.…”

Enantioselective Tandem Oxidation/Michael–Aldol Approaches to Tetrasubstituted Cyclohexanes

“…From this point of view, the use of a metal‐catalyzed oxidation of allylic alcohols in a stereoselective cascade constitutes a valuable strategy to readily access enals . Recently, 1,2‐dihydroquinolines have been synthesized via combining catalytic oxidative cycles with iminium–enamine catalysis . If the catalytic oxidation of allylic alcohols is compatible with our proposed tandem Michael–aldol, it will contribute to the development of a novel oxidative Michael–aldol process (Scheme ), thereby providing a new synthetic approach for enantioselective construction of cyclohexanes with interesting architectures.…”

“…[13] Recently,1 ,2-dihydroquinolines have been synthesized via combining catalytic oxidative cycles with iminium-enamine catalysis. [14] If the catalytic oxidation of allylic alcohols is compatible with our proposed tandem Michaelaldol,i tw illc ontribute to the development of an ovel oxidative Michael-aldol process (Scheme1), thereby providing an ew synthetic approach for enantioselective construction of cyclohexanes with interesting architectures. Herein, we report the tandem oxidation/Michael-aldol approaches for the synthesis of cyclohexanes with four stereocenters.…”

Asymmetric one-pot reactions using heterogeneous chemical catalysis: recent steps towards sustainable processes

“…Thus, their application in one-pot reactions also evolved rapidly. [51][52][53][54][55][56] As a consequence, one-pot processes using heterogeneous organocatalyts, either in combination with soluble catalysts or using multifunctional catalytic materials became one of the preferred ways of increasing the sustainability of preparation of chiral fine chemicals. Due to the larger numbers of such materials, it was expedient to subdivide this section according to the type of immobilized organocatalyst.…”