The singlet and triplet excited states of diphenylvinylene carbonate (V) react with vinyl ethers to produce 2 + 2 cycloadducts. Weak exciplex emission is observed when the fluorescence of V is quenched by high concentrations of 2-methyl-1-methoxypropene. Rate constants for fluorescence quenching and limiting quantum yields for singlet cycloaddition increase with decreasing vinyl ether ionization potential, in accord with an exciplex mechanism for cycloaddition. The solvent dependence of the cycloaddition quantum yields is indicative of a moderately polar exciplex. Singlet addition to the isomeric 1-methoxypropenes is stereospecific, whereas triplet addition proceeds with substantial loss of stereochemistry. Comparison of solvent effects and adduct stereochemistry for the singlet and triplet addition reactions suggests that a triplet exciplex is the precursor of a triplet biradical intermediate.
ASJC Scopus subject areas
- Colloid and Surface Chemistry