Categories: C-F Bond Formation >
Synthesis of difluoroalkanes
Bis(2-methoxyethyl)aminosulfur trifluoride (Deoxo-Fluor reagent) is a new deoxofluorinating agent that is much more thermally stable than DAST (C2H5)2NSF3. It is effective for the conversion of alcohols to alkyl fluorides, aldehydes and ketones to the corresponding gem-difluorides, and carboxylic acids to the trifluoromethyl derivatives with, in some cases, superior performance compared to DAST.
G. S. Lal, G. P. Pez, R. J. Pesaresi, F. M. Prozonic, H. Cheng, J. Org. Chem., 1999, 7048-7054.
Aminodifluorosulfinium tetrafluoroborate salts act as efficient deoxofluorinating reagents when promoted by an exogenous fluoride source and, in most cases, exhibited greater selectivity by providing less elimination byproduct as compared to DAST and Deoxo-Fluor. Aminodifluorosulfinium tetrafluoroborates are storage-stable, and unlike DAST and Deoxo-Fluor do not react violently with water.
F. Beaulieu, L.-P. Beauregard, G. Courchesne, M. Couturier, F. LaFlamme, A. L'Heureux, Org. Lett., 2009, 11, 5050-5053.
Easily prepared 2-alkyl-1,3-dithiane derivatives were reacted with BrF3 to form the corresponding 1,1-difluoromethyl alkanes in good yield. The reaction proceeds well with primary alkyl halides. The limiting step for secondary alkyl halides is the relatively low yield of the dithiane preparation.
R. Sasson, A. Hagooly, S. Rozen, Org. Lett., 2003, 59, 3635-3641.
A desulfurizing difluorination reaction of benzyl sulfides having an electron-withdrawing group such as an ester, a ketone, a nitrile, or an amide in the presence of IF5 gave gem-difluoro compounds in good yield.
T. Fukuhara, S. Hara, Synlett, 2009, 198-200.
Sodium bromodifluoroacetate (BrCF2CO2Na) is an effective difluorocarbene source for high-yielding synthesis of gem-difluorocyclopropanes and gem-difluorocyclopropenes under mild conditions.
K. Oshiro, Y. Morimoto, H. Amii, Synthesis, 2010, 2080-2084.