Preparation of 1-Choro-1-fluoroethylenes via Chlorofluorocarbene

Fluorinated Carbenes

“…[312][313][314] These methods of carbene generation were used to prepare 1-chloro-1-fluoroethenes. 315 An initial study reported that chlorofluorocarbene, generated from dichlorofluoromethane with potassium tert-butoxide, reacted with triphenylphosphine to form (chlorofluoromethylene)triphenylphosphorane (78), which subsequently reacted with benzophenone to yield 1-chloro-1-fluoro-2,2-diphenylethene (40%). 316 In the study by Yamanaka and co-workers, a wide variety of additional carbonyl compounds were used with the yields of the alkenes ranging from 63% for the reaction with p-ClC 6 H 4 CHO to 8% with PhCOMe (eq 56).…”

Fluorinated Ylides and Related Compounds

“…6 Subsequent work by Ando provided a useful route to chlorofluoromethylene olefins via an ylide route. 53 These workers generated chlorofluorocarbene from methyl dichlorofluoroacetate in the presence of triphenylphosphine as outlined in eq 52. Aromatic aldehydes and activated ketones gave higher yields than nonactivated ketones.…”

“…The work of Speziale, 6 Ando, 53 and Krutzsch 55 (section 4.1) demonstrated that chlorofluorocarbene could be captured by triphenylphosphine to give a stable solution of the chlorofluoromethylene ylide (eq 69). Even at higher temperatures the chlorofluoromethylene ylide exhibited some stability.…”

Reactions Involving Hetero Atoms

“…(97). The radical intermediates derived from CBr 4 , CBr 2 Cl 2 , CHBr 3 , and CHI 3 , however, will eliminate Br* (or I·) rather than rearrange (231).…”

“…The direct photolysis of dimethyl diazomalonate in the presence of y-methylallyl choride also proceeded with allylic inversion to give amethylallyl chloromalonate [97] and the cyclopropane [96] (233). Relative rates indicate that singlet bis(methoxycarbonyl)carbene attacks bromine and sulfur atoms about two times faster than it attacks chlorine in an allylic position.…”