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Communication | Special issue | Vol 103, No. 1, 2021, pp.205-217
Published online, 19th October, 2020
DOI: 10.3987/COM-20-S(K)24
■ Rhodium-Catalyzed Crossed [2+2+2] Cycloaddition with Ynamides: Key-Strategy for the Concise Total Synthesis of 3-Oxygenated Carbazole Alkaloids

Carole Alayrac* and Bernhard Witulski*

*Laboratoire de Chimie Molèculaire et Thioorganique (LCMT) , National Graduate School of Engineering and Research Center, France

Abstract

Total syntheses of a set of naturally occurring 3-oxygenated carbazole alkaloids - 6-chlorohyellazole, carazostatin, carbazomycins A and B - are described. The key-strategy underlines a highly chemo- and regioselective rhodium-catalyzed [2+2+2] cyclotrimerization between appropriately tailored yne-ynamides and 1-methoxypropyne that is stirred by the interplay of stereoelectronic and steric effects allowing the introduction of four ring substituents of the natural carbazoles within a single step and making the overall syntheses short and efficient.