Reactions of alkynes and carbene equivalents with oxo(salen)chromium(V) complexes

Article abstract of DOI:10.1021/ja00063a010

Alkynes are oxidized by oxo(salen)chromium(V) triflate and related complexes 2 to form 1,2-diones. The oxidation of diphenylacetylene proceeds by formation of an intermediate which reacts more rapidly with a second equivalent of oxometal complex to form benzil. The intermediate is most likely a metallaoxetene or a related species, such as a metallocarbene. Reactions of phosphorus or nitrile ylides with 2 proceed to form carbonyl compounds (and phosphine oxide or nitrile) in a manner consistent with participation of similar intermediates. The reactions appear to be related mechanistically to alkene epoxidation by the same oxometal complexes.