Density functional theory investigation of the ruthenium-catalyzed cycloisomerization of silicon-tethered 1,7-enynes

Abstract

Density functional theory calculations at the M06-2X/6-31G(d,p) (RECPs for Ru) level of theory are performed to explore the reaction mechanism for the cycloisomerization of silicon-tethered 1,7-enynes using CpRuCl as a catalyst. The solvent effect is taken into account by M06-2X/6-311++G (d,p) single-point calculations with SMD solvation model in toluene. The calculation results indicate that the reactions of the ruthenium-catalyzed cycloisomerization of 1,7-enynes occur through the possible mechanisms and get five-membered ring or six-membered ring products, respectively. The process of forming six-membered ring product is more favored kinetically with the barrier of 13.6kcal/mol for Ph group, while the energy barrier for five-membered ring product becomes relatively higher of 34.3kcal/mol. The above reaction mechanism indicates that the ruthenium-catalyzed cycloisomerization of silicon connected 1,7-enynes has high regioselectivity, which is consistent with the experimental observations of Kaminsky and Clark.