Reactions with asymmetrical diarylethylenes and diarylethanes. Part XI. Rearrangement reactions of 1,1-di-p-alkoxyphenyl-2,2-dihalogenoethanes in boiling ethylene glycol alone or in the presence of sodium 2-hydroxyethoxide

Abstract

1,1-Di-p-alkoxyphenyl-2,2-dibromoethanes are readily converted by boiling ethylene glycol into the corresponding 4,4′-dialkoxystilbenes and the cyclic acetals of 4,4′-dialkoxydiphenylacetaldehydes with the liberation of hydrogen bromide. Longer heating gives the corresponding 4,4′-dialkoxy-diphenylacetaldehydes, -deoxybenzoins, and -benzophenones. The latter three classes are also formed on heating solutions of the acetals in acidified ethylene glycol.

The structure of the acetals has been confirmed by their syntheses from 4,4′-dialkoxydiphenylacetaldehydes and ethylene glycol in the presence of hydrogen chloride.

Heating the equimolecular quantities of the 1,1-di-p-alkoxyphenyl-2,2-dihalogenoethanes and sodium 2-hydroxyethoxide in ethylene glycol gives the corresponding deoxybenzoins, while increasing the ratio of the reagent gives the acetylenes.