Reactivity of 2,2-difluoro-3-methyl-3-butenal toward some O-, N- and C-nucleophiles

Abstract

Addition of nucleophiles to 2,2-difluoro-3-methyl-3-butenal (I) is complicated by its spontaneous polymerization. Compound I afforded neither hydrate nor dimethyl acetal but reacted with ethylene glycol to give the cyclic acetal II. Reaction with acetyl chloride and acetic anhydride led to the respective acetate III and diacetate IV. Satisfactory reaction with N-nucleophiles was observed only in the case of hydroxylamine and dinitrophenylhydrazine. Diethylamine reacted with I only at 150 °C to give the reduction product VI and the ethylaldimine VII. The compound I added nitromethane and sodium cyanide (giving X and XI, respectively); the adducts or products of their reduction with lithium aluminium hydride were hydroxylated at the double bond to give analogues of alcoholic sugars with difluoromethylene group in position 3. Hydroxylation of the butenal I or the acetate III afforded 3,3-difluoro-2,4-dihydroxy-4-methyloxolane (XIX) which was prepared also by cleavage of the acetal XVIII obtained from II by hydroxylation. Addition of bromine to the double bond in III and IV gave the dibromo derivatives XV and XVI; the attempted replacement of bromine in XV and XVI by acetate anion failed. Bromination of I in aqueous medium afforded 3-bromo-2,2-difluoro-3-methyl-4-butanolide (XIV).