Transformation of ketones and aldehydes to gem-dihalides via hydrazones using copper(II) halides

Preparation of gem-dihalides by the oxidation of hydrazones, which were easily prepared by the treatment of ketones and aldehydes with hydrazine hydrate in the presence of molecular sieves 4A, with copper(II) compounds was studied. The treatment of hydrazones with copper(II) bromide-lithium tert-butoxide in THF gave the corresponding gem-dibromides in good yields. gem-Dichlorides were also obtained by the similar reaction of hydrazones using copper(II) chloride-lithium tert-butoxide as an oxidizing agent. Furthermore it was found that the same transformations were conveniently achieved by the use of copper(II) halides-triethylamine in methanol. Copyright (C) 1996 Elsevier Science Ltd