Intramolecular reactions of diazocarbonyl compounds provide access to cyclopropanes. Methylcyclopropane, like many other cyclopropanes, undergoes ring-opening reactions. Carbenes add to double bonds to form cyclopropanes. As with other cyclopropanes, ring tension results in a relatively unstable compound. Substituted cyclopropanes also react, following Markovnikov's rule. It leaves epoxides unaffected, but affects cyclopropanes occasionally. There exist a handful of examples of ring contractions from cyclobutanones to cyclopropanes. Alkylidenecyclopropanes more readily undergo C-C bond oxidative addition than cyclopropanes. In addition, the ring structures of cyclopropanes/enes and cyclclobutanes/enes offer very little conformational flexibility. Cyclopropanes can be obtained by a variety of intramolecular cyclisation reactions. Being highly strained, cyclopropanes are prone to oxidative addition to transition metal complexes.