Cycloaddition of Carbodiimides and Triphenylketen-imine to Allenic Acids. Preliminary Communication

Allenic acids are found to add to dicyclohexylcarbodiimide affording, in the presence of secondary amines, the 1,3-oxazine-4-ones. 5 . Under neutral conditions, they add to diaryl- or aryl(cyclohexyl)carbodiimides and triphenylketen-imine to give the corresponding tricyclo[5.2.2.0^1,5]undecatriene-3-ones 7–9 and 12 .