Competitive 1,2- and 1,5-hydrogen shifts following 2-vinylbiphenyl photocyclization

Frederick D. Lewis*, Meledathu C. Sajimon, Xiaobing Zuo, Michael Rubin, Vladimir Gevorgyan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

The photocyclization of 2-vinylbiphenyl and its derivatives has been proposed to occur via a two-step mechanism: photocyclization to form an unstable 8a,9-dihydro-phenanthrene intermediate, followed by exothermic unimolecular isomerization to a 9,10-dihydrophenanthrene. The mechanism of the hydrogen shift process has been investigated using deuterated derivatives of 2-isopropenylbiphenyl and 2,6-diphenylstyrene. 1H NMR analysis of the photoproducts indicates that the thermally allowed 1,5-hydrogen or deuterium shift is a minor product-forming pathway and that an unusual double 1,2-hydrogen or deuterium shift is the major product-forming pathway. The potential energy surface for photocyclization and hydrogen shift processes has been explored computationally. The calculated barrier for the 1,5-shift is predicted to be significantly lower than that for the 1,2-shift. Alternative mechanisms for the occurrence of 1,2-hydrogen or deuterium migration are presented.

Original languageEnglish (US)
Pages (from-to)10447-10452
Number of pages6
JournalJournal of Organic Chemistry
Volume70
Issue number25
DOIs
StatePublished - Dec 9 2005

ASJC Scopus subject areas

  • Organic Chemistry

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