Vinyltriphenylphosphonium salt mediated synthesis of 1,4-benzoxazine and coumarin derivatives

Protonation of the reactive 1:1 intermediate produced in the reaction between triphenylphosphine and dimethyl acetylenedicarboxylate by 2-aminophenol, 3-aminophenol, 4-aminophenol and 2-amino-3-hydroxypyridine leads to vinyltriphenylphosphonium salts, which undergo Michael addition with the conjugate base of the aminophenol or aminohydroxypyridine to produce highly functionalized heterocyclic compounds.