Room temperature preparation of α-chloro-β,β-difluoroethenylzinc reagent (CF2CClZnCl) by the metallation of HCFC-133a (CF3CH2Cl) and a high yield one-pot synthesis of α-chloro-β,β-difluorostyrenes

An efficient dehyrohalogenation method for the synthesis of α,β,β-trifluorostyrenes, α-chloro-β,β-difluorostyrenes and E-1-arylperfluoroalkenes

“…The reaction was worked up after completion and the crude product obtained was purified either by fractional distillation using an 8 cm vigreux column or by column chromatography. All the 1-chloro-2,2-trifluorostyrenes prepared were fully characterized and were in agreement with the spectral data of the styrenes prepared by an alternative method [22,24].…”

“…Recently, we have developed a remarkable room temperature preparation of 1,2,2-trifluorostyrene by the metallation of the readily available HFC-134a (Scheme 1) [20,21]. This methodology was successfully extended to the synthesis of various 1-halo-2,2-difluorostyrenes from CF 3 CH 2 X (X = Cl, Br, I) type precursors [22][23][24].…”

Fluorinated Organozinc Reagents

“…Kumadaki and coworkers recently reported the use of CF 3 CHClBr (Halothane) as a precursor to [F 2 C=CClZnCl] (equation 31); however, the yield of the zinc reagent was not reported 17 . Although Kumadaki reports reasonable yields of coupled products employing Halothane as a precursor, this precursor in our hands did not cleanly give high yields of the zinc reagent (equation 32) 18 .…”

“…These workers examined the reaction of a wide variety of organolithium bases with the cheap, commercially available CF 3 CFH 2 (HFC-134a) in the presence of anhydrous zinc salts. They established that LDA and anhydrous zinc chloride could effectively react with CF 3 CFH 2 to produce good yields of the trifluorovinylzinc reagent at ambient temperatures 19,20 (15)(16)(17)(18)(19)(20) • C) (equation 33). The in situ production of trifluorovinylzinc from CF 3 CFH 2 was based on previous reports by Coe and coworkers 21 -23 .…”

“…Typical examples of this class of styrenes, where X = Cl, are cited in equation 35 16,18 . Disubstituted analogs could also be prepared, as illustrated in equations 36-38.…”