A novel synthesis of 1,3-oxazine-2,4-diones via a simple and efficient reaction of CO2 with 2,3-allenamides.

A simple and efficient reaction of CO(2) with 2,3-allenamides under mild conditions (CO(2) balloon without any metal catalyst in the presence of K(2)CO(3) or Cs(2)CO(3)) leads to an efficient synthesis of 1,3-oxazine-2,4-diones. The high reactivity of the allene moiety is crucial for the success of this transformation since the corresponding reaction of alpha,beta-unsaturated alkenamides or alkynamides does not occur.