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Transition Structures of the Electrocyclic Reactions of cis,cis,cis ‐1,3,5‐Cyclooctatriene
Author(s) -
Thomas Bert E.,
Evanseck Jeffrey D.,
Houk Kendall N.
Publication year - 1993
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.199300035
Subject(s) - conrotatory and disrotatory , chemistry , electrocyclic reaction , ring (chemistry) , computational chemistry , stereochemistry , organic chemistry
The electrocyclic reactions of cis,cis,cis ‐1,3,5‐cyclooctatriene have been studied using ab initio molecular orbital theory. cis,cis,cis ‐1,3,5‐cyclooctatriene can undergo an electrocyclic ring opening in a conrotatory fashion to form cis,cis ‐1,3,5,7‐octatetraene and a disrotatory electrocyclization to form bicyclo[4.2.0]octa‐2,4‐diene. The transition structures for these electrocyclic reactions have been located. Geometry optimizations employed restricted Hartree‐Fock calculations and the 3–21G and 6–31G* basis sets. Electron correlation energies were calculated using second‐order, and in some cases fourth‐order, Møller‐Plesset theory. Scaled RHF/6–31G* force constants were employed in the prediction of secondary deuterium isotope effects for the conrotatory ring opening. The ground state of cis,cis,cis ‐1,3,5‐cyclooctatriene exists in a twist‐boat conformation with staggering at the saturated linkage. The transition structure for the conrotatory electrocyclic ring opening to form cis,cis ‐1,3,5,7‐octatetraene has a helical structure, which has implications for the stereoselectivities of ring closure of 1‐substituted‐ cis,cis ‐1,3,5,7‐octatetraenes. The disrotatory transition structure for the electrocyclization to form bicyclo[4.2.0]octa‐2,4‐diene is strongly distorted from C s symmetry, in contrast to the transition structure for the disrotatory electrocyclization of cis ‐1,3,5‐hexatriene. This distortion is caused by staggering about the saturated linkage.