Theoretical study of mechanism of cycloaddition reaction between 2,2-dimethyl(2-germavinylidene) [(CH_3)_2Ge=C:] and formaldehyde

摘要

The mechanism of the cycloaddition reaction between singlet 2,2-dimethyl(2-germavinylidene) [(CH_3)_2Ge=C:] and formaldehyde has been investigated with CCSD(T)//MP2/6-311G**method. From the potential energy profile, it could be predicted that the reaction has two competitive dominant reaction pathways. The first pathway consist of the transfer of formaldehyde oxygen π-electrons to the 2p unoccupied orbital of the C: atom in 2,2-dimethyl(2-germavinylidene) with a formation of intermediate which then isomerizes to a four-membered heterocyclic ring carbene (Ge and O in the 1,3-position). The second pathway is a direct [2 + 2] cycloaddition reaction in which the interaction of two π-bonds in 2,2-dimethyl(2-germavinylidene) and formaldehyde generates another four-membered heterocyclic ring carbene (Ge and O in 1,2-position). Because of the unsaturated property of the C: atom in the two four-membered heterocyclic ring carbenes, the two four-membered heterocyclic ring carbenes could further react with formaldehyde, generating two spiro-heterocyclic ring compounds.