Thermal decomposition of O-benzyl ketoximes; role of reverse radical disproportionation

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DOIResolve DOI: http://doi.org/10.1039/b313491a
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TypeArticle
Journal titleOrganic and Biomolecular Chemistry
ISSN1477-0520
Volume2
Issue3
Pages415420; # of pages: 6
SubjectChemical bonds; Dissociation; Free radicals; Hydrogen; Pyrolysis; Solvents; Temperature; Abstraction; Benzaldehyde; Benzyl ketoximes; Dihydroanthracene; Dihydrophenanthrene; Enamine tautomers; Oxime ethers; Reverse radical disproportionation reaction; Tetralin; Thermolyses; Organic compounds
AbstractThermolyses of seven dialkyl, two alkyl-aryl and two diaryl O-benzyl ketoxime ethers, R1R2C=NOCH2Ph, have been examined in three hydrogen donor solvents: tetralin, 9,10-dihydrophenanthrene, and 9,10-dihydroanthracene. All the oxime ethers gave the products expected from homolytic scission of both the O-C bond (viz., R1R2C=NOH and PhCH3) and N-O bond (viz., R1R2C=NH and PhCH2OH). The yields of these products depended on which solvent was used and the rates of decomposition of the O-benzyl oxime ethers were greater in 9,10-dihydrophenanthrene and 9,10-dihydroanthracene than in tetralin. These results indicated that a reverse radical disproportionation reaction in which a hydrogen atom was transferred from the solvent to the oxime ether, followed by β-scission of the resultant aminoalkyl radical, must be important in the latter two solvents. Benzaldehyde was found to be an additional product from thermolyses conducted in tetralin. This, and other evidence, indicated that another induced decomposition mode involving abstraction of a benzylic hydrogen atom, followed by β-scission of the resulting benzyl radical, became important for some substrates. Participation by minor amounts of enamine tautomers of the oxime ethers was shown to be negligible by comparison of thermolysis data for the O-benzyloxime of bicyclo[3.3.1]nonan-9-one, which cannot give an enamine tautomer, with that of the O-benzyloxime of cyclohexanone.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21276707
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Record identifier87d92376-5886-4508-9dc7-e99a8c7e72f1
Record created2015-10-13
Record modified2016-05-09
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