Electrochemically induced free-radical tandem cyclisation of chlorodifluoromethylated ketones Application to the synthesis of gem-difluorinated heterocycles
P. Hapiot et M. Medebielle, Electrochemically induced free-radical tandem cyclisation of chlorodifluoromethylated ketones Application to the synthesis of gem-difluorinated heterocycles, J FLUORINE, 107(2), 2001, pp. 285-300
The synthesis of a series of chlorodiffuoromethylated ketones 1-6 is presen
ted and the cyclic voltammetry of the reductive cleavage of these ketones w
as investigated, in N,N-dimethylformamide (DMF), at an inert electrode. Ind
irect electrochemical reduction (by means of an electrogenerated anion radi
cal) in acetonitrile (CH3CN) or in N,N-dimethylformamide (DMF), of the naph
thalene-derived chlorodifluoroacetylated compounds 1 and 2 in the presence
of the olefinic substrates 7-10, yields new gem-difluoro heterocyclic compo
unds 11-16 after intramolecular cyclisation of a gamma,gamma -difluoroalkyl
radical. Aromatic nucleophilic substitution of alpha,alpha -difluoroketone
s 12 and 13, in anhydrous dimethylsulfoxide, with several tetramethylammoni
um salts of imidazole as nucleophiles, proceeds under mild conditions to gi
ve the corresponding nitrogen-nitrogen exchanged products 17-23 in moderate
to good yields. (C) 2001 Elsevier Science B.V. All rights reserved.