Siladifluoromethylations and difluoromethylations on sp(3), sp(2), and sp carbons of lithiated carbamates, arenes, and terminal alkynes, respectively, have been attained by employing the Ruppert-Prakash reagent (CF3TMS) and fluoroform (CF3H) as the CF2 sources. The advantage of this reaction is that the (sila)difluoromethylated compounds can be obtained by simple treatment of easily accessible substrates, lithium bases, and CF3TMS or CF3H. Furthermore, the products bearing the TMS group can be transformed into the valuable compounds with the CF2 fragment via the carbon-carbon bond forming reactions.
The catalytic difluoromethylation of arylzinc reagents with difluoroiodomethane in the presence of Pd2(dba)3/Xantphos is described to produce difluoromethyl products. Mechanistic investigations reveal that the oxidative addition of difluoroiodomethane to [(Xantphos)Pd0] provides trans‐[(Xantphos)PdII(I)CF2H], which is subsequently transformed to cis‐[(Xantphos)PdII(Ph)CF2H] through transmetalation of phenylzinc. Next, reductive elimination occurs (t1/2=44.7 min at −10 °C) to give PhCF2H. The structural changes in [(Xantphos)PdII(Ph)CF2H] from trans to cis facilitates reductive elimination of PhCF2H.
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