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The vapor phase photochemistry of the three isomeric cyanopyridines and the three methylpyridines was studied by irradiating their vapors at 254 nm. It was found that direct irradiation of any one cyanopyridine isomer resulted in the formation of the other two isomers of cyanopyridine or methylpyridines respectively. The reactivity of each isomer was found to be different. This was suggested to be based on the stability of their azaprefulvene intermediates formed during interconversion. The phototransposition of these molecules was suggested to result from 2,6-bonding, nitrogen migration around the five sides of cyclopentenyl ring followed by rearomatization. This mechanism was found to be consistent with the results of deuterium labeling studies of cyanopyridines These result suggest that cyanopyridines undergo phototransposition via the intermediacy of azaprefulvenes instead of Dewar-pyridine and azaprismane. Thus, photochemical studies showed that the six trideuteriopyridine isomers constitute two separate photochemical triads. Each triad consists of three isomers that are photointerconverting upon irradiation at 254 nm in the vapor phase. Similary, it was found that the three isomeric tetradeuteriopyridine isomers also constitute a photochemical triad and are interconverting upon irradiation at 254 nm in the vapor phase. These phototranspositions are best explained by the cyclization, nitrogen migration, and rearomatization mechanism. These results are in contrast to the long-held belief that pyridine is photostable in the vapor phase. Instead, unlabeled pyridine undergoes a hidden phototransposition leading back to itself.

In this paper, some of the work by Talbott has been repeated and other reactions of 4-picoline and pyridine N-oxides with aromatic halogen compounds have been investigated.

Deux sujets indépendants ont été traités dans ce manuscrit.Dans une première partie a été étudiée la possibilité d'obtenir des synthons chiraux à partir de la pyridine. Pour cela nous avons dans un premier temps développé une méthode originale de quaternisation des sels de pyridium et d'imidazoliums grâce à une réaction de Mitsonubu. Par la suite, des 2-aminopyridines ont été substituées puis engagées dans une réaction de quaternisation-réduction conduisant à des composants saturés. Malheureusement, des composés n'ont pu conduire aux synthons linéaires envisagés.Dans une seconde partie, nous nous sommes intéressés au développement d'un nouveau type de peptidomimétique dans lequel le lien amide est remplacé par un cycle imidazolique, ceci dans la continuité de travaux menés dans notre équipe. Dans un premier temps, nous nous sommes focalisés sur la mise au point de conditions efficaces menant au mime considéré. Cette méthodologie nous a permis la synthèse de plusieurs dipeptides. / Two different topics will be discussed in this work.In the first part has been studied the possibility to obtain chiral building-blocks from pyridine. For this purpose, we intially developed an original method for quartenization of pyridium and imidazolium salts through a Mitsonubu reaction. Then, 2-aminopyridines were substituted and then engaged in a quaternization-reduction reaction, leading to satured compounds. Unfortunately, these compounds have not leaded to targeted linear building-blocks.In a second part, we have been interested in the deveopment of a new peptidomimetic family in which the amide bond is replaced by an imidazole ring, extension of previous work in our research group. Initially we focused on the development of conditions leading to considered mimic. This methodology has allowed us the synthesis of several dipetides incorporating our mimic with good results. The determination of acido-basic properties of these structures has also been investigated.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy