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Title: Thermal reactions of 1,2-diazepines
Author: Stefaniuk, Edward
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1976
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This thesis is concerned with the thermal reactions of 3H-1, 2-benzodiazepines and 1H-2, 3-benzodiazepines, and the acid-catalysed reactions of 1H-2, 3-benzodiazepines. The study of the thermolysis in aprotic media of IH-2, 3-benzodiazepines revealed two modes of decomposition each proceeding by a 1, 5-sigmatropic hydrogen migration leading to 5H-diazepines or hydrocarbon products. From deuterium-labelling studies the hydrocarbon products were shown to have been derived from a carbene intermediate. A kinetic study of the thermolysis of two 1H-diazepines yielded values for the Arrhenius activation energy and for the thermodynamic parameters 4G° and 4S*. These values were compared with literature values for related compounds and evidence was produced for decomposition which involves a sigmatropic migration as the rate determining step. The acid-catalysed decompositions of 1H-2, 3-benzodiazepines in benzene was carried out, and the formation of the hydrocarbon products is rationalised in terms of carbonium ions which could be trapped in ethanol leading to ethers. The solution phase thermolysis of 1, 2, 3, 3a-tetrahydro-l0-phenylbenzo[c]cyclopenta[f][1, 2]diazepine was followed by high pressure liquid chromatography (h. pal. c.) as well as being subject to a product study. The mechanism for the decomposition involves a diazo-intermediate which leads to one major product - 3-diphenylmethylenecyclopentene. Kinetic studies in hexadecane and benzonitrile showed that the diazepine was the precursor to the products and that the isomerisation to 3-1'-cyclopentenyl-3-phenylindazole was merely an equilibration without the indazole leading to major products. Solvent effects and decomposition of the diazepine in the presence of tributylphosphine gave evidence against dipolar intermediates for the equilibration process, and suggested either a radical pathway or a concerted step. The synthesis of a series of 3H-indazoles from the corresponding 3H-diazepines is described, and the structures of the indazoles was deduced from their proton and carbon-13 n.m.r. and mass spectral data.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available