An efficient one‐pot synthesis of pyrimido[2,1‐b][1,3]oxazine derivatives via the reaction of isocyanides with dialkyl acetylenedicarboxylates in the presence of 5‐substituted uracils

The reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and dialkyl acetylenedicarboxylates was trapped by uracil and its 5‐substituted derivatives to yield highly functionalized pyrimido2,1‐b]1,3]oxazine derivatives in fairly good yields. J. Heterocyclic Chem.,(2011).