The conformational equilibria of 1- and 2-phenyl-1,2-dihydronaphthalene

✍ Scribed by J. J. M. Lamberts; W. H. Laarhoven

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 290 KB
• Volume: 102
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19831020310

✦ Synopsis

Abstract

The conformational equilibria of 1‐ and 2‐phenyl‐1,2‐dihydronaphthalene (1 and 2) have been studied using 500 MHz ^1^H NMR spectroscopy.

The signals due to the protons at C(1) and C(2) of compound 2 and of a deuterated derivative of 1 (3,4‐d~2~‐1) were analysed as ABX patterns. The fraction x of the conformer, having the phenyl group in a pseudo‐axial (pa) position, was found to be 0.44 for 3,4‐d~2~‐1, in contrast to the marked preference shown by non‐aromatic substituents at C(1) of 1,2‐dihydronaphthalenes for the pa position. This difference is most probably due to π‐overlap between a pseudo‐equatorial phenyl substituent and the aromatic moiety of the 1,2‐dihydronaphthalene counterbalancing the peri‐interaction with H(8).

For 2, x = 0.31, indicating a slight preference of the phenyl group for the pseudo‐equatorial (pe) position which preference is also observed for other substituents at C(2) of 1,2‐dihydronaphthalenes.