Hexafluoroacetone and Methyl Trifluoropyruvate Acylimines in the Cyelocondensation with Amides

摘要

Fluorinated 1,3,5-oxadiazines comprise a promising class of biologically active substances, including, for example, effective insecticides and fungicides of a general action [1]. There are two approaches to the synthesis of these compounds. The first is based on the Diels-Alder aza-reaction of acylimines with hexafluoroacetone or methyl trifluoropyruvate with nitriles [2, 3] or cyanamines [4-7]. The second route is dehydration under rigid conditions (heating in oleum) of amidals derived from the hexafluoroacetone perfluoro-acylimines and amides of perfluorocarboxylic acids [8]. Thus, the availability of the 1,3,5-oxadiazines through the cycloaddition reaction is determined primarily by the availability of nitriles, and their synthesis by the dehydration in rigid conditions is applicable to a limited number of amides, in particular, to the amides of perfluorocarboxylic acids. The aim of this study was to expand the possibilities of cyelocon-densation reactions of hexafluoroacetone and methyl trifluoropyruvate acylimines with carboxylic amides to produce a variety of 1,3,5-oxadiazines containing one or two trifluoromethyl groups. A prerequisite for this research were the data we obtained in the course of systematic studies of the behavior of N-substituted hexafluoroacetone and methyl trifluoropyruvate imines in cyelocondensation reactions with 1,3-binucleophiles, including the use of a system of pyridine-thionyl chloride as a dehydrating agent [9].