Propargylic Alcohols as Three-Carbon Synthons in a Rhodium-Catalyzed Heteroannulation via a Merged C-H Functionalization and Cascade Cyclization Process

We report herein, an unprecedented reactivity of propargyl alcohols as a “Three-Carbon Synthon” in the synthesis of core structures of isocryptolepine, g-carbolines, dihydrochromeno[2,3-b]indoles and diindolylmethane's (DIM) derivatives. The transformation involves a rhodium(III)-catalyzed C-H functionalization, heteroannulation of indoles followed by cascade cyclization with external as well as internal nucleophiles to afford diverse products. The reaction features highly effective transformations involving two C-C, two C-N and two C-O bonds, leading to the formation of a variety of molecular frameworks that are a part of several biologically active natural products.