6-OXOCYCLOHEXA-2,4-DIENYLIDENEKETENE - A HIGHLY REACTIVE ALPHA-OXOKETENE

The title ketene 2 has been generated by laser flash photolysis and ob served in solution for the first time, using time-resolved infrared sp ectroscopy. The kinetics of the reactivity of 2 with H2O, MeOH, and Et 2NH with relative reactivities of 1.0, 2.0, and 73 have been measured. These are the first direct measurements of the reactivities of a kete ne with these different nucleophiles under the same conditions. Ab ini tio molecular orbital calculations indicate the hydration occurs by in -plane attack of the H2O molecule on the ketenyl carbonyl through a ps eudopericyclic transition state with assistance by coordination to the keto-carbonyl.