Structures and Rotational Barriers of a Diiodobinorsnoutane: Energetic Preference for Gauche Conformation

Joseph P Herres; Caitlin A Moran; Mark A Forman; James E Hall; John P McCauley Jr; Don E Pivonka; Steven S Wesolowski

doi:10.1021/acs.joc.6b01204

Structures and Rotational Barriers of a Diiodobinorsnoutane: Energetic Preference for Gauche Conformation

J Org Chem. 2016 Aug 5;81(15):6862-6. doi: 10.1021/acs.joc.6b01204. Epub 2016 Jul 21.

Authors

Joseph P Herres¹, Caitlin A Moran¹, Mark A Forman¹, James E Hall², John P McCauley Jr², Don E Pivonka², Steven S Wesolowski²

Affiliations

¹ Department of Chemistry, Saint Joseph's University , 5600 City Avenue, Philadelphia, Pennsylvania 19131, United States.
² AstraZeneca Pharmaceuticals, 1800 Concord Pike, Wilmington, Delaware 19850, United States.

PMID: 27391283
DOI: 10.1021/acs.joc.6b01204

Abstract

The diiodobinorsnoutane, bi(5-iodopentacyclo[4.3.0.0(2,4).0(3,8).0(5,7)]non-4-yl) (5), exists in a sterically hindered gauche conformation rather than an anti or an averaged (freely rotating) C2v structure. Density functional theory (DFT) predictions place the gauche conformation 11 kcal/mol more stable than the anti conformation with a barrier of 17 kcal/mol connecting the minima. These are consistent with variable-temperature NMR (17.1 ± 0.8 kcal/mol) estimates and X-ray analysis. Predictions of the torsional profiles of the yet-unsynthesized bromo-, chloro-, and fluoro- analogues show a progressive lowering of the barriers.

Publication types

Research Support, Non-U.S. Gov't