In our development of convergent routes to 1,2,3-trisubstituted all-cis cyclopropanes, we were interested in the synthesis of dimethylester substituted cyclopropanes.

Diester substituted cyclopropanes can be rapidly accessed by reaction of alkenes with malonate-derived carbenoids. However, despite significant recent advancements in the area of metal-catalyzed cyclopropanations, the reaction of alkenes with these less reactive carbenoids remains a significant challenge.

We found that dirhodium a,a,a',a'-tetramethyl-1,3-benzenedipropanoate [Rh₂(esp)₂] is a superior catalyst for this reaction. The versatility of the cyclopropanation methodology was demonstrated with an unprecedented array of alkenes, including electron-poor styrenes, nitrile substituted alkenes, sterically hindered aliphatic alkenes and alkynes. The experimental protocol is remarkably simple, uses readily available diazomalonates and requires only stoichiometric amounts of alkene substrates.