In the title compound, C(11)H(8)BrNO(2), the nine-membered fused-ring is nearly planar [maximum deviation = 0.022 (2) Å] and the allyl group is arched over the nine-membered fused-ring at a dihedral angle of 89.2 (1)°. Weak inter-molecular C-H⋯O hydrogen bonding is present in the crystal structure.

Reactions of benzoylpyruvate with a mixture of aromatic aldehydes and 5-amino-1,3,4-thiadizole-2-thiol in a 1:1:1 molar ratio, afforded 5-(5-aryl-4-benzoyl-3-hydroxy-2-oxo-2,5-dihydro-1H-pyrrol-1-yl)-1,3,4-thiadizole-2-thiols (3a-c). The structure of the resulted products was confirmed by determination of the melting point and spectrophotometric techniques such as IR and 1H-NMR spectroscopy.