Ab Initio Study of Intramolecular Ring Cyclization of Protonated and BF3-Coordinated trans- and cis-4,5-Epoxyhexan-1-ol

• Published in: Journal of organic chemistry Vol. 64; no. 15; pp. 5530 - 5541
• Main Authors: Coxon, James M, Thorpe, Aaron J
• Format: Journal Article
• Language: English
• Published: American Chemical Society 23.07.1999
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo990364d

The potential energy surface for the rearrangement of cis- and trans-4,5-epoxyhexan-1-ol with acid and the Lewis acid BF3 to five- and six-membered cyclic ethers has been investigated by ab initio methods. The transition structures involving both inversion and retention of configuration at the reaction center at the HF/6-31G* and B3LYP/6-31G* levels are characterized. The preference for furan formation over pyran is attributed to the more favorable O−Cep−O bond angles at the transition structures for furan formation. The torsional O−Cep−Cep−O angles associated with tetrahydrofuran and tetrahydropyran formation vary with structure and do not directly correlate with the preferred pathway.