UVM Theses and Dissertations
Format:
Print
Author:
Javed, Muhammad Irfan
Dept./Program:
Chemistry
Year:
2009
Degree:
Ph. D.
Abstract:
This dissertation describes the development of new methods for the synthesis nitrogen gen-containing compounds by the reactions ofhydrazones with sulfonium salts. Activated dimethyl sulfoxide efficiently dehydrogenates hydrazones to the respective diazo compounds at low temperature. Under optimized reaction conditions, triethylamine hydrochloride quantitativley precipitates from the reaction mixture and is removed by filtration to provide solutions of diazo compounds. Treating these solutions with carboxylic acids provided esters in good yield. Alternatively, stable diazo compounds were isolated as solids. This method is easily scalable and provided analytical grade diphenyldiazomethane in 93% yield on 109 scale.
Under similar reaction conditions, a-chloroazo compounds were easily prepared in high yields by the reaction of corresponding aryl hydrazones with chlorodimethylsulfonium chloride. These a-chloroazo compounds were precursors to bicyclic diazenium hexachloroantimonates which were efficiently prepared by a Lewis acid mediated intramolecular cycloaddition. Tenninal olefins provided mixtures of ring fused and bridged bicyclic diazenium salts and electron-deficient alkenes successfully participated in the cycloaddtion reaction.
Under more milder reaction conditions, bicyclic diazenium triflates were prepared in good yield directly from the hydrazones by reaction with dimethyl sulfide ditriflate at -78°C. In situ variable temperature NMR study of the reaction indicated that a critical temperature was achieved between -30°C and -20°C, during which time most of the diazenium salt was fonned. The yields of diazenium triflates were estimated by adding an internal NMR statndard to the crude reaction mixture.
Under similar reaction conditions, a-chloroazo compounds were easily prepared in high yields by the reaction of corresponding aryl hydrazones with chlorodimethylsulfonium chloride. These a-chloroazo compounds were precursors to bicyclic diazenium hexachloroantimonates which were efficiently prepared by a Lewis acid mediated intramolecular cycloaddition. Tenninal olefins provided mixtures of ring fused and bridged bicyclic diazenium salts and electron-deficient alkenes successfully participated in the cycloaddtion reaction.
Under more milder reaction conditions, bicyclic diazenium triflates were prepared in good yield directly from the hydrazones by reaction with dimethyl sulfide ditriflate at -78°C. In situ variable temperature NMR study of the reaction indicated that a critical temperature was achieved between -30°C and -20°C, during which time most of the diazenium salt was fonned. The yields of diazenium triflates were estimated by adding an internal NMR statndard to the crude reaction mixture.