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Abstract The first enantioselective formal 4+2 cycloadditions of 3‐nitroindoles are presented. By using 3‐nitroindoles in combination with an organocatalyst, chiral dihydrocarbazole scaffolds are formed in moderate to good yields (up to 87 %) and enantioselectivities (up to 97 % ee ). The reaction was extended to include enantioselective 4+2 cycloadditions of 3‐nitrobenzothiophene. The reaction proceeds through a 4+2 cycloaddition/elimination cascade under mild reaction conditions. Furthermore, a diastereoselective reduction of an enantioenriched cycloadduct is presented. The mechanism of the reaction is discussed based on experimental and computational studies.
Li et al. (Fri,) studied this question.