Recent approaches to the synthesis of tetrahydrocarbazoles.

The tetrahydrocarbazole (THC) motif is ubiquitous in natural products and biologically active compounds. THCs can serve as favorable synthetic intermediates or precursors en-route to desired complex natural products. Despite a considerable number of strategies for the synthesis of THCs that have emerged in the last two decades, only a handful of reviews have been published on the subject. Herein, we have summarized synthetic methodologies published in the last ten years for the benefit of organic chemists. The review focuses on non-enantioselective syntheses of THCs, and encompasses ring opening reactions of donor-acceptor cyclopropanes, metal-catalyzed C-C/C-N bond formation, cycloaddition, conjugate addition, and miscellaneous reactions employed for accessing the THC framework.