Synthesis of .alpha.,.alpha.-Difluoro-Functionalized Ketones
摘要:
In the presence of a catalytic amount of tetrakis(triphenylphosphine) palladium [Pd(PPh(3))(4)], iododifluoromethyl alkyl and phenyl ketones 1 react with alkenes to give the corresponding alpha,alpha-difluoro-gamma-iodo ketones in high yields at room temperature either neat or in hexane at 60 degrees C. A variety of functional groups, such as alkyl, trimethylsilyl, hydroxy, epoxy, ketone, and ester, are tolerated under the reaction conditions. The reaction can be completely suppressed by a radical inhibitor, di-tert-butyl nitroxide or hydroquinone. A ring closure reaction occurs when 1 reacts with diethyl diallylmalonate in the presence of a catalytic amount of Pd(PPh(3))(4). Under UV irradiation, the reaction of 1 with diallyl ether gives a tetrahydrofuran derivative. All these results are consistent with a radical chain mechanism initiated by single electron transfer from Pd(PPh(3))(4) to 1. In the presence of a catalytic amount of nickel dichloride hexahydrate, the iodine in the 1:1 addition adducts is readily reduced by zinc in moist THF under mild conditions to give the corresponding alpha,alpha-difluoro ketones in high yields. A one-pot addition-reduction reaction has been developed for the synthesis of alpha,alpha-difluoro ketones without the isolation of the 1:1 addition adducts, which provides a new, efficient, and practical method for the preparation of a variety of alpha,alpha-difluoro-functionalized ketones.
Visible Light-Promoted Phosphine-Catalyzed Difluoroalkylation of Arenes and Heterocycles
作者:Heng Lu、Dong-yu Wang、Ao Zhang
DOI:10.1021/acs.joc.9b02882
日期:2020.1.17
A visible light-promoted difluoroalkylation reaction of arenes or heterocycles, using triaryl phosphine as the catalyst and difluoroalkyl iodide as the alkylating agent, is presented. The strategy is highlighted by photocatalyst-free, mild reaction conditions and a broad substrate scope. Mechanistic experiments indicate that this reaction involves a radical-chain process that is initiated by an electron
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.
with excellent stereoselectivity. The 1‐benzoyldifluoromethyl‐2,2‐diphenylethylene products synthesized through a radical reaction process are versatile synthons for the construction of various fluorine‐containing compounds, which have antiproliferative activity on human tumor cells.