Synthesis of putative clausenal from carbazole using sequential C–H borylations

Abstract

A synthesis of the putative clausenal structure has been achieved from commercially available carbazole using a five-step sequence that features three iridium-catalyzed C–H borylation reactions. This conceptually disparate approach to carbazole synthesis further demonstrates the utility of the iridium-catalyzed borylation reaction in heteroaromatic C–H functionalization. The spectroscopic data of the synthetic sample casts doubt on the structure assigned to the natural product.