The Adverse Effect of Benzannelation on the Aromaticity of Oxocinyl Anion: A Combined Experimental and Theoretical Study

✍ Scribed by Hamid S. Kasmai; Xiaodong Wang; Hanh-Nhon Doan; Josef F. Femia; Thad M. Yablonsky; Mary E. Read; David T. Dutton

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: German
• Weight: 318 KB
• Volume: 93
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200900430

✦ Synopsis

Abstract

A synthesis of 2__H__‐1‐benzoxocin from readily available compounds was accomplished. The potentially ‘aromatic’ π‐excessive systems 2__H__‐1‐benzoxocinyl and 6__H__‐dibenz[b,f]oxocinyl anions were generated from their corresponding conjugate acid precursors 7c and 8, respectively. It was found that 2__H__‐1‐benzoxocinide 3d lacks the type of π‐frame stability associated with the parent 2__H__‐oxocinide 1d and that the dibenzo analog 5b is more unstable than 3d. Both 3d and 5b undergo rapid structural reorganization to form their corresponding stable isomeric anions. We were able to characterize the proton‐quenched products of these anions as the ring‐opened structures 15 and 18, respectively. ^1^H‐NMR and an ab initio calculation at the 6‐31g* level indicated that, unlike the ‘aromatic’ parent 2__H__‐oxocinide 1d and the aza analog 3c, 3d incorporates a non‐planar oxocinyl ring in which the negative charge is primarily localized on the pentadienyl moiety of the ring, but also partial delocalization of π‐electron density onto the benzene ring occurs.