Executive Summary : | Organocatalytic enantioselective desymmetrization of simple prochiral molecules has been recognized as a reliable method to construct highly factionalized scaffold with multiple chiral centres in a single step. Therefore, tremendous attention has been given to the organocatalytic enantioselective desymmetrization for an efficient construction of carbocycles. Desymmetrization of 2,5-cyclohexadienones is highly challenging and there has been a growing interest in the recent decades to develop methods to access enantiomerically enriched scaffolds presented in several pharmaceuticals and natural products. Cyclohexa-2,5-dienones are usually isolable and stable prochiral synthetic intermediates to undergo a large number of dissymmetric transformations. The most straight synthetic route to access 2,5-cyclohexadienones is the oxidative dearomatization of a 4-substituted phenol using commercially available oxidizing agents such as PhI(CH3CO2)2 or PhI(CF3CO2)2 and 2- iodoxybenzoic acid (IBX).
Over the last 20 years, many transition-metal catalyzed and organocatalyzed enantioselective conjugate additions, 1,2-additions, and cycloadditions on prochiral 2,5-cyclohexadienones have been developed. Among them, organocatalyzed enantioselective desymmetrization is one of the most powerful strategies for the efficient construction of the nonracemic scaffolds. Despite remarkable advances, very limited approaches have been developed in the area of organocatalytic enantioselective desymmetrization of 2,5-cyclohexadienones. Therefore, in this scenario, the novel strategies and methodologies delineated in the proposed organocatalytic enantioselective cascade Michael reactions providing highly enantioenriched tetrahydroindole, tetrahydrofuran and 1,4-dioxane derivatives, which are frequently found in pharmaceuticals and biologically active natural products. |