Reaction of 2- heterosubstituted oxiranes and some other studies.

Abstract

The object of the present investigation is the study of the synthetic and mechanistic aspects of the rearrangement of 2?halooxiranes to ??halocarbonyl compounds. The thesis entitled “Reactions of 2?Heterosubstituted Oxiranes and Some Other Studies” is divided into six chapters. Chapter I reviews the literature pertaining to the rearrangement of 2?heterosubstituted oxiranes (1) to ??heterocarbonyl compounds, with emphasis mainly on their synthetic applications. An attempt to develop a new method for 1,2?carbonyl transposition based on the rearrangement of 2?halooxiranes to ??halocarbonyl compounds was taken up (Scheme I). This prompted the study of some interesting debromination–reduction reactions of ?,??dibromoketones, which were discovered during these studies. This is discussed in Chapter II. The preparation of ??chloroaldehydes using the strategy shown in Scheme II, which involves the above?mentioned rearrangement, is dealt with in Chapter III. However, this reaction was limited to R = Me, Ph, Bz, because of the novel finding that reduction of ?,??dichloroketones by ??hydrogen transfer from Grignard reagents was particularly favoured. Chapter IV discusses the synthesis of dissymmetrically substituted ??chloroaldehydes according to the strategy shown in Scheme III, which is an extension of the strategy described in Chapter III. Reduction of ?,??dichloroketones by Grignard reagents having ??hydrogen atoms was confirmed. The chloroaldehyde synthesis, however, is synthetically useful, with yields being fair to good. Chapter V describes a study of nucleophilic additions to 2?acetoxyoxiranes to obtain ??substituted ketones. This study is again based on the rearrangements of 2?heterooxiranes and allows the synthesis of many ??substituted ketones, which are otherwise rather inaccessible. Chapter VI describes the reaction of some oximes with benzenediazonium chloride, in which unusual products were obtained. The mechanism of formation and their structures (A and B) are discussed.