A step-economical divergent approach to isoflavenes based on Suzuki-Miyaura cross coupling of a 3-boryl-2H-chromene with aryl bromides: application to total synthesis of isoflavonoid natural products

Abstract

We present a step-economical divergent synthetic approach for isoflavene derivatives using the Suzuki-Miyaura cross coupling of a 3-boryl-2H-chromene and three aryl bromides. 3-Boryl-2H-chromene, which is not a well-explored species, was prepared via Miyaura-Ishiyama borylation of a 3-chloro-2H-chromene obtained through a Claisen rearrangement cyclization cascade reaction. Further conversion of the cross-coupling products, three isoflavene derivatives, afforded three isoflavonoid natural products with one or two additional reaction steps.

Keywords: Claisen rearrangement; Suzuki–Miyaura cross coupling; cascade reaction; isoflavonoid; total synthesis.