Article citationsMore>>

A. L. J. Beckwith, T. Lawrence and A. K. Serelis, “Stereoselectivity of Ring Closure of Substituted Hex-5-enyl Radicals,” Journal of the Chemical Society, Chemical Communications, Vol. 1980, No. 11, 1980, pp. 484-485. doi:10.1039/c39800000484

has been cited by the following article:

• TITLE: Computational Study of the Cyclization of 5-Hexenyl, 3-Oxa-5-Hexenyl and 4-Oxa-5-Hexenyl Radicals

  AUTHORS: Albert R. Matlin, Matthew C. Leyden

  KEYWORDS: Radical Cyclizations; Activation Energies; UB3LYP; UCCSD (T)

  JOURNAL NAME: International Journal of Organic Chemistry, Vol.3 No.3, August 27, 2013

  ABSTRACT: The intramolecular cyclization of 5-hexenyl radicals continues to be an important synthetic method for the construction of five-membered rings. The synthetic utility arises from the high degree of regioselectivity to give predominantly cyclopentyl products in high yield under mild conditions. Recently we reported product cyclization studies on 4-oxa perturbed 5-hexenyl radical. In this paper, we report our results from a computational study (UB3LYP and UCCSD (T)) of the cyclization of a series of 5-hexenyl and 3-and 4-oxa-5-hexenyl radicals. Three highly conserved cyclization tran-sitions states (exo-chair, exo-boat and endo-chair) were located for 10 acyclic radicals. Activation energies were calcu-lated for the three modes of cyclization for each radical. Calculated values for the exo/endo cyclization ratios had a high level of agreement with experiment and predictions were offered for two cases that have not been experimentally tested. The increased percentage of exo-cyclization with 3-and 4-oxa substitution is the result of an increase in the energy dif-ference between the exo-and endo-chair transition states compared to the hydrocarbon systems. The decreased rate of cyclization of the 4-oxa compounds is primarily due to the stabilization of the initial acyclic radical by the vinyl ether linkage. The increase in the rate of cyclization with 3-methyl substitution is due to the increased conformational energy of the starting acyclic radical.