A THEORETICAL COMPARISON OF 2 COMPETING DIRADICAL CYCLIZATIONS IN ENYNE-ALLENES - THE MYERS-SAITO AND THE NOVEL C-2-C-6 CYCLIZATION

The reaction mechanism and the energetics of the C-2-C-7 and of the C- 2-C-6 cyclization of (Z)-1,2,4-heptatriene-6-yne are studied employing large scale MR-CI calculations. In addition the influence of vibratio nal motions and of temperature corrections on the barrier height of bo th reactions is estimated. For both products the first excited electro nic states are computed to estimate possible switches from diradical t o zwitterionic reaction mechanism.