Conformations of highly hindered aryl ethers: XXIII–PMR evidence for preferred conformations and intramolecular π complex formation in nitrophenyl naphthyl ethers

✍ Scribed by Pedro A. Lehmann F.

• Publisher: John Wiley and Sons
• Year: 1974
• Tongue: English
• Weight: 463 KB
• Volume: 6
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270060115

✦ Synopsis

Abstract

The PMR spectrum of 2‐bromo‐4,6‐dinitrophenyl 2′‐naphthyl ether (1) is consistent with the preferential adoption of a twist conformation (1a) in which the 6‐nitro group and the 1′‐hydrogen are located endo to the ether link. This preference is explained by the formation of an intramolecular π complex between the 6‐nitro group and the C1′C2′ bond, which is stronger than that formed with the C2′C3′ bond, in accord with their bond orders. This study adduces further evidence in favor of: (a) the adoption of twist conformations by these and related ethers, (b) the importance of intramolecular π complex formation as a conformational influence, (c) the formation of complexes in such cases is with specific portions of, and not the complete, π cloud and (d) indicates that similar effects may be discerned in analogous ethers related to the thyroid hormones.