A Branched Domino Reaction: Asymmetric Organocatalytic Two-Component Four-Step Synthesis of Polyfunctionalized Cyclohexene Derivatives

摘要

Traditionally, domino reactions are defined as processes of two or more bond-forming reactions, in which the subsequent transformation takes place at the functionalities obtained in the former transformation under identical reaction condi-tions. In linear domino reactions, the progress of the former step will always affect that of the next steps (Figure 1a). Among the domino/cascade reactions, organocata- lytic enantioselective reactions have been developed at a remarkable pace after the revitalization of the field of organocatalysis. However, we planned to develop another kind of domino reaction, which we call a "branched domino reaction" (Figure 1b). In this domino sequence, the starting material can be used in two parallel reactions at the same time under identical conditions to generate two intermediates, which will then act as reactants in the next reaction step to form the desired product. In this version, the progress of the first step will have no effect on the second step, and higher overall yields could be achieved. This will enable the efficient synthesis of complex molecules from a few simple starting materials in an ecologically and economically manner.