Electrocyclic reactions of 1-substituted 1,3,5,7-octatetraenes. An ab initio molecular orbital study of torquoselectivity in eight-electron electrocyclizations

The effects of substituents on the conrotatory electrocyclizations of 1-substituted cis,cis-1,3,5,7-octatetraenes have been studied with ab initio molecular orbital theory. The results are compared to the conrotatory electrocyclic ring openings of 3-substituted cyclobutenes. Geometry optimizations employed restricted Hartree-Fock calculations and the 3-21G basis set. Electron correlation energies were calculated using second-order MOller-Plesset theory and the 6-31 G * basis set. The transition structure for the conrotatary electrocyclization of cis,cis-1,3,5,7-octatetraene has a helical structure