Synthesis of α-Halo-α,α-difluoromethyl Ketones by a Trifluoroacetate Release/Halogenation Protocol
摘要:
Three series of alpha-halo-alpha,alpha-difluoromethyl ketones are prepared from highly alpha-fluorinated gem-dials by exploiting the facile release of trifluoroacetate, followed by immediate trapping of the liberated alpha,alpha-difluoroenolate with an electrophilic chlorine, bromine, or iodine source. The products are typically isolated in good yields, even in the case of sensitive, alpha-iodo-alpha,alpha-difluoromethyl ketones. Also, we demonstrate that an alpha-iodo-alpha,alpha-difluoromethyl ketone will participate in a copper-promoted reaction to forge a new carbon-carbon bond.
Cu(I)‐catalyzed three‐component reaction of 2‐iodo‐2,2‐difluoroacetophenones, alkynes, and TMSCN for the synthesis of useful difluoroacyl‐substituted nitriles is described. This method has broad substrate scope and excellent stereoselectivity. Preliminary mechanistic investigation indicated that a radical‐mediated process was involved in this cyanodifluoroalkylation reaction.
A palladium-catalyzedone-pot difunctionalization of alkynes with α,α-iododifluoroacetones is introduced for the synthesis of difluorinated 1,3-enynes. The reaction proceeds through the radical addition of RCOCF2 radical to alkynes and subsequent Sonogashiracoupling with the same alkynes to give the 1,3-enyne products with high regio and stereoselectivity.
Ni‐catalyzed radicaldifunctionalization of alkenes with iododifluoromethylketones was realized for the synthesis of α,α‐difluoroketones. This reaction can also be used for the construction of analogs containing 5‐membered heterocycles through radical addition and sequenced cyclization reactions.