Efficient Preparation of TMSCCl2Br and Its Use in Dichlorocyclopropanation of Electron‐Deficient Alkenes

The reaction of excess TMSCl and LiCCl₂Br at low temperature is a technically simple high yield route to TMSCCl₂Br. The latter is a stable source of the dichlorobromomethide carbanion, which undergoes 1,4‐addition with cyclic nitroalkenes and (E)‐fumarates leading to dichlorocyclopropanes after bromide expulsion. For nitrostyrenes the reaction arrests at the 1,4‐addition product. Low temperature NMR spectroscopy studies and DFT calculations suggest the formation of an “ate” species [(nitronate)SiFMe₃]^? which, upon boil‐off of TMSF at 10–20 °C, yields the cyclopropane. DFT calculations also support the experimental differences between fluoride and acetate as promotors.     

Complexes of rhodium carbonylchloride and phosphorus(iii) cyanides in mediated electrochemical reduction of 2-carbomethoxy-2-methyl-1,1-dichlorocyclopropane

Electrochemical reduction of the complexes Rh(CO)ClL₂ [L = (EtO)₂PCN (1), Ph₂PCN (2)] and Rh₂(CO)₄L [L = P(CN)₃ (3), (4)] and their catalytic properties in electrochemical reduction of 2-carbomethoxy-2-methyl-1,1-dichloro-cyclopropane were studied. The catalytic electroreduction of a substrate at the reduction potentials of the central ion was developed for complexes2–4. This process is accelerated substantially for complexes2 and3 in the presence of anthracene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1970–1972, October, 1995.