“…Alkenylboronic esters 101,102 , N-silylated allylamines 171 and acetylenes 172,173 are successfully cyclopropanated with diazocarbonyl compounds under catalysis of one of those metal derivatives. Newly developed metallic catalysts for diazoacetic esters include polymer-bound, quantitatively recoverable Rh(II) carboxylate salts 174 186 . The stereochemical integrity of the alkenes, however, may not be retained.…”