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Title:Preparation and Cycloaddition Reactions of Oxazoline Nitrogen Oxides
Author(s):Ashburn, Stephen Patrick
Department / Program:Chemistry
Discipline:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Chemistry, Organic
Abstract:Oxazoline N-oxides have been prepared in medium to high yields under mild conditions by condensation of 2-(hydroxyamino)-2-methyl-1-propanol with ortho esters or amide acetals. 3 + 2 Cycloaddition reactions of the oxazoline N-oxides and the related pyrroline N-oxides with phenyl isocyanate, dimethyl acetylenedicarboxylate, methyl phenylpropiolate, phenylpropiolonitrile, methyl acrylate, and acrylonitrile were carried out. The reaction of 4,4-dimethyl-2-phenyloxazoline N-oxide with acetylenic dipolarophiles in concentrated solutions of dimethylamine hydrochloride in dichloromethane, however, led to the formation of isoxazoles. Competitive experiments demonstrated that 2,4,4-trimethyloxazoline N-oxide is at least 6,800 times more reactive toward phenyl isocyanate than the analogous 2,5,5-trimethylpyrroline N-oxide, and is 160 times more reactive toward dimethyl acetylenedicarboxylate than the pyrroline N-oxide. Rate constants for the 3 + 2 cycloaddition reactions of 4,4-dimethyl-2-phenyloxazoline N-oxide and 5,5-dimethyl-2-phenylpyrroline N-oxide with phenyl isocyanate and dimethyl acetylenedicarboxylate were measured. These data indicate that the oxazoline N-oxide is approximately 76,000 times more reactive toward phenyl isocyanate than the pyrroline N-oxide, and is 70 times more reactive toward dimethyl acetylenedicarboxylate than the pyrroline N-oxide. An explanation for the enhanced reactivity of oxazoline N-oxides is forwarded on the basis of frontier molecular orbital theory.
Issue Date:1985
Type:Text
Description:191 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
URI:http://hdl.handle.net/2142/70288
Other Identifier(s):(UMI)AAI8511575
Date Available in IDEALS:2014-12-15
Date Deposited:1985


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