Theoretical study of the mechanism of cycloaddition reaction between dichloromethylene silylene and formaldehyde

摘要

The mechanism of cycloaddition reaction between singlet dichloromethylene silylene and formaldehyde has been investigated using a MP2/ 6-31G* method, including geometry optimization and vibrational analysis for the stationary points on the potential energy surface. The energies of different conformations are calculated by CCSD(T)//MP2/ 6-31G* method. From the potential energy profile, it can be predicted that the cycloaddition reaction between singlet dichloromethylene silylene and formaldehyde has three competitive dominant reaction channels: (1) the two reactants first form a highly strained three-membered ring intermediate INT1c, which then isomerizes to an active four-membered ring product P1 via a transition state TS1c by ring-increasing reaction; Subsequently, P1 further reacts with formaldehyde to form the more stable silapolycyclic product P2; (2) the two reactants first form a fourmembered ring intermediate INT1b by the [ 2+2] cycloaddition reaction, which then isomerizes to the four-membered ring product P3.1 via a transition state TS3.1, resulting from the chlorine transfer reaction; (3) INT1b further reacts with formaldehyde to form a silapolycyclic intermediate INT4, which then isomerizes to a silapolycyclic product P-4 via a transition state TS4.