| Summary: | The dehydrogenation of 3-phenyl-2,6-diphenyl-iminopiperidine has been studied under a variety of conditions, leading to a new synthesis of 2,3'-bipyridyls and to a new synthetic route to 2,6-diaminopyridines from readily available glutaro-nitriles. A novel 3-aryloxypiperidine intermediate has been isolated from the dehydrogenation of 3-phenyl-2,6-diphenyliminopiperidine with 3,3',5,5'-tetrachloro-4,4'-diphenoquinone. Methyl homologues of 3-phenyl-2,6-diphenyliminopiperidine have been prepared and their reactions under dehydrogenating conditions studied, to help confirm the structure of the 2,3'-bipyridyl. A high yield synthesis of 2,6-di-imino-3-phenylpiperidine has been found but its dehydrogenation proved unsuccessful. Investigation of alpha-alkylideneglutaronitriles and their condensations with amines has opened up a further route to the preparation of 2,6-di-aminopyridines. The reactions of 3-phenyl-2,6-diphenylimino- piperidine under dehydrogenating conditions, together with spectra of fixed-bond analogues have helped to further elucidate its fine structure. Glutaronitriles have been condensed with diamines to produce three-unit materials but none of these afforded macrocyclic or polymeric materials when further condensations were attempted. Ethylene-diamine afforded an imidazoline on condensation with glutaronitriles in addition to the expected three-unit product, while o-phenylenediamine underwent an analogous reaction in which the sole product was a benzimidazole. No reaction could be achieved between glutaronitrile and 1,3-di-imino-isoindoline, the only products of the reaction being a mono amide of tricyanophenine and phthalo cyanine. Condensations between glutaronitriles and active methylene compounds have been carried out and extended to the formation of methine-linked macrocyclic products, but attempts to dehydrogenate the two- and three-unit products have been unsuccessful. The mass-spectra of the glutaronitriles, di-iminopiperidines, and diaminopyridines prepared in this thesis are discussed in detail. Nucleophilic additions to nitriles and the cyclization of dinitriles, particularly with amines and active methylene compounds, have been reviewed up to the completion of this work in 1969.
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