Synthesis of Carbazoles and Dihydrocarbazoles by a Divergent Cascade Reaction of Donor–Acceptor Cyclopropanes

An alkylation/olefination cascade of indolecarboxaldehydes and phosphonate-functionalized donor–acceptor cyclopropanes affords functionalized dihydrocarbazoles and cyclohepta­[cd]­indoles in formal (3 + 3) and (4 + 3) cycloadditions. A minor modification to the reaction conditions also allows access to the fully aromatic heterocyclic scaffolds by thermal loss of an electron-rich aryl moiety.吲哚甲醛与膦酸酯官能化供体-受体环丙烷（donor–acceptor cyclopropanes）的烷基化/烯化级联反应，可通过形式(3+3)与(4+3)环加成过程，生成官能化二氢咔唑与环庚并[cd]吲哚。对该反应条件进行小幅调整后，还可通过热解脱除一个富电子芳基基团，从而得到全芳香族杂环骨架。