Iminoacyl Halides and Oxy Functions

Abstract

This chapter describes the preparation of iminoacyl halides; imidoyl halides (including N-phosphorylated imidoyl halides), hydroxamoyl halides, and hydrazonyl halides and their oxy analogues; imidic acids, N-haloimidates, hydroxamic acid esters, N-organothioiminoesters, hydrazonoates, N-phosphorylated iminoesters, trialkylsilylimidates and mixed anhydrides from carboximidic acids and organic or inorganic acids. The most common preparative routes for the iminoacyl halides involve the halogenation of a range of precursors — amides are halogenated to give imidoyl chlorides, aldoximines, hydroxamic acids, and nitroalkanes or nitroalkenes to give hydroxamoyl halides, and hydrazides or hydrazones to give hydrazonyl halides. There are a variety of preparative methods for imidic acid esters including; the Pinner synthesis (the reaction of an alcohol and a nitrile under acid catalysis), the acylation or transimination of simpler N-unsubstituted imidates, and the ring-opening of heterocycles. Organothioimidoyl ester derivatives include sulphonylimidoyl esters, the corresponding sulphinylimidoyl esters, and their sulphenyl analogues. The sulphonyl derivatives are the most studied and are readily prepared by the treatment of the appropriate sulphonamide with an orthoester. One of the most common routes to hydrazonoates is via the reaction of hydrazidoyl halides (especially chlorides) with alkali metal alkoxides, while trialkylsilylimidates are readily obtained by the silylation of carboxylic acid amides.