Iron-Catalyzed Cyclopropanation in 6 M KOH with in Situ Generation of Diazomethane

Abstract

Tamer Triangulations Diazomethane is a broadly useful precursor to carbene (CH 2 ), which, in turn, reacts with olefins to form triangular carbon cycles known as cyclopropanes. These small rings are of fundamental interest for their strained bonds and turn up periodically in natural products, as well as in pharmaceutical and agrochemical research. Unfortunately, the flip side of diazomethane's facile reactivity is its dangerous tendency to explode—a hazard exacerbated by the need to isolate the compound after its preparation in highly basic water before it can be reacted with hydrophobic olefins. Morandi and Carreira (p. 1471 ) now show that an iron cyclopropanation catalyst can circumvent the need for the isolation step, inducing reaction of the hazardous compound in a biphasic aqueous/organic medium immediately after its generation.