Ph3P-mediated one-pot synthesis of functionalized 3,4-dihydro-2H-1,3-thiazines from N,N′-dialkylthioureas and activated acetylenes in water

A one-pot synthesis of alkyl 3,4-dihydro-4-oxo-2H-1,3-thiazine-6-carboxylates from dialkyl acetylenedicarboxylates and N,N'-dialkylthioureas in the presence of triphenylphosphine (20 mol%) is described.