The stereoselective synthesis of α,α-difluoro-β-hydroxyketones of high enantiomeric purity is described starting from opticallyactiveα,α-difluoro-β-hydroxy esters. The esters were converted to the corresponding N-methoxy-N-methyl amides, which were treated with Grignard and organolithium reagents to provide the α,α-difluoro-β-hydroxyketones with up to 100% ee.
substoichiometric amount of chiral Lewis acid 2 or 3 provides the corresponding α,α-difluoro β-hydroxyesters 4–12 with high enantioselectivities (up to 98% ee). Reaction temperature has a great influence on the enantiofacial selection of aldehydes; the reactions of benzyloxyacetaldehyde catalyzed by Lewis acid 2 at −78 and −30°C gave the (+)- and (−)-α,α-difluoro β-hydroxyesters 7 in optical yields of 98% and
Decarboxylative arylation with diaryliodonium(<scp>iii</scp>) salts: alternative approach for catalyst-free difluoroenolate coupling to aryldifluoromethyl ketones
α-Aryl-α,α-difluoroketones were synthesized via decarboxylative arylation using diaryliodonium salts under catalyst-free conditions without organometallic intermediates. The products can be transformed into various difluorinated functional groups.