Iron-Catalyzed Dealkenylative Borylation of Alkenes via Ozonolysis

Abstract

Given the exceptional versatility of boronic esters as synthetic linchpins, strategies that directly transform naturally abundant motifs such as alkenes into boron-containing intermediates offer substantial value. Herein, we report the development of a dealkenylative borylation transformation that converts C(sp3)–C(sp2) bonds into C(sp3)–B bonds via ozonolysis and iron catalysis. This protocol proceeds efficiently while tolerating a broad range of functional groups. Mechanistic studies indicate that the borylation reagent bis(catecholato)diborane (B2cat2) serves a dual purpose as both the boron source and the stoichiometric reductant. We demonstrate synthetic utility by applying this dealkenylative borylation reaction directly to naturally occurring steroids, terpenes, and terpenoids, as well as to the synthesis of natural products. Finally, the potential of our alkene-to-boron transformation to rapidly access structurally diverse analogues from feedstock compounds is highlighted through the divergent functionalization of the alkene-containing natural product betulinic acid.