CONVENIENT PROCEDURES FOR CONVERSION OF CARBONYL COMPOUNDS TO gem-DIFLUOROOLEFINS AND THEIR SELECTIVE REDUCTIONS TO MONOFLUOROOLEFINS

Abstract

The in situ reaction of dibromodifluoromethane, triphenylphosphine, and aldehydes in the presence of zinc dust affords good yields of gem-difiuoroolefins. Reduction of the difluoroolefins gives selectively the corresponding monofluoro-olefins in excellent yields. The scope and limitation of these procedures are described and compared with those of previous methods.

Synthesis and Horner−Wittig Chemistry of (Fluoromethyl)diphenylphosphane Oxide

“…Some routes depending on α-heterosubstituted (fluoromethyl)phosphorus intermediates have been quite successful. 1,1-Difluoroalkenes, obtained from CBr 2 F 2 and HMPT [2] or from (difluoromethyl)diphenylphosphane oxide, [3] could be reduced selectively to give monofluorinated alkenes. [2] Fluorovinyl sulfones, accessible in high yields by HornerϪWadsworthϪEmmons chemistry, have been desulfurized with aluminum amalgam [4] or by use of organotin chemistry.…”

“…1,1-Difluoroalkenes, obtained from CBr 2 F 2 and HMPT [2] or from (difluoromethyl)diphenylphosphane oxide, [3] could be reduced selectively to give monofluorinated alkenes. [2] Fluorovinyl sulfones, accessible in high yields by HornerϪWadsworthϪEmmons chemistry, have been desulfurized with aluminum amalgam [4] or by use of organotin chemistry. [5] The classical Wittig reaction with (fluoromethyl)diphenylphosphonium salts gave only moderate yields and lacked stereoselectivity.…”

Fluorinated Analogues of Amicetose and Rhodinose – Novel Racemic and Asymmetric Routes

“…We also removed the benzyl ether from a mixture of 19 and 20 by hydrogenolysis in ethanol to afford (an inseparable mixture of) 23 and 24 in good yield. Monofluoro analogues of both pyranosides could be approached by reductive defluorination [28,29] of 7, which afforded a mixture of alkene diastereoisomers 24 and 25. Hydrolysis and reduction afforded a mixture of anti-and syn-diol monobenzyl ethers 26 and 27 (Scheme 6).…”

Transition Metal-Mediated and Metal-Catalyzed Carbon–Fluorine Bond Formation

“…While fluoroalkene synthesis is often accomplished using Wittig-type reactions [191][192][193][194][195], several examples have been reported using gold catalysis and alkyne substrates. Gold-catalyzed hydrofluorination of alkynes was first demonstrated by the Sadighi group, using TREAT•HF (Fig.…”