Myers-Saito and Schmittel cyclization of hepta-1,2,4-triene-6-yne: A theoretical REKS study

Spin-restricted ensemble-referenced Kohn-Sham (REKS) calculations have been performed on the cyclization process of hepta-1,2,4-triene-6-yne leading t o a five-membered ring (Schmittel cyclization) or a six-membered ring (Myer s-Saito process), both products being biradicals. Geometries compare well w ith density functional as well as ab initio calculations and experimental m easurements from the literature. Relative energies and singlet-triplet gaps were studied and compared with BCCSD(T) calculations.