Categories: C-F Bond Formation >
Synthesis of difluoroalkanes
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Recent Literature
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.
Related
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.
