NHC-catalyzed generation of difluorocarbene from trimethylsilyl 2,2-difluoro-2-(fluorosulfonyl)acetate (TFDA) enables the synthesis of enol difluoromethyl ethers starting from cyclohexenones and tetralones. The resultant enol difluoromethyl ethers were successively dehydrogenated with DDQ to furnish aryl difluoromethyl ethers in good to high yield.

Ruthenium-catalyzed C-H arylation of aromatic nitriles with arylboronates is described. The use of RuH(CO){P(4-MeCH)} as a catalyst provided higher yields of the ortho arylation products than the conventional RuH(CO)(PPh) catalyst. The arylation takes place mostly at the ortho positions, but unprecedented para arylation was also partially observed to give ortho,para diarylation products. In addition to C-H bond cleavage, the cyano group was also found to function as a directing group for cleavage of C-O bonds in aryl ethers.

Controlled generation of difluorocarbene was effected by an NHC catalyst under mild conditions starting from trimethylsilyl 2,2-difluoro-2-fluorosulfonylacetate (TFDA). Cyclohexenones and tetralones were treated with TFDA in the presence of catalytic amounts of N,N'-dimesitylimidazolium chloride and sodium carbonate. The ketones were difluoromethylated with the generated difluorocarbene to afford enol difluoromethyl ethers without difluorocyclopropanation. The ethers thus obtained were dehydrogenated with DDQ to furnish aryl difluoromethyl ethers in high yield. Under similar conditions, secondary amides underwent difluoromethylation selectively on the oxygen atom to give difluoromethyl imidates, which allows the formation of 2-difluoromethoxypyridines.

No abstract

Cyclic and acyclic ketones are difluoromethylated with difluorocarbene which is derived from difluoroacetate (II) through its controlled generation in the presence of an N‐heterocyclic carbene activator.