Affordable Access

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

Authors
  • Lewis, Frederick D
  • Sajimon, Meledathu C
  • Zuo, Xiaobing
  • Rubin, Michael
  • Gevorgyan, Vladimir
Type
Published Article
Journal
The Journal of organic chemistry
Publication Date
Dec 09, 2005
Volume
70
Issue
25
Pages
10447–10452
Identifiers
PMID: 16323856
Source
Medline
License
Unknown

Abstract

[reaction: see text] 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.

Report this publication

Statistics

Seen <100 times