9-Furfuryl­idene-2,3-dimethyl-6,7,8,9-tetrahydro-4H-­thieno[2′,3′:4,5]pyrimidino[1,2-a]pyridin-4-one

The title compound, C(17)H(16)N(2)O(2)S, was obtained by condensation of 2,3-dimethyl­thieno[2′,3′:4,5]pyrimidino[1,2-a]pyridin-4-one with furfural in the presence of sodium hydroxide. One of the methyl­ene groups of the tetra­hydro­pyrido ring is disordered over two positions in a 0.87 (1):0.13 (1) ratio. The thieno[2,3-d]pyrimidin-4-one unit and the furan ring are both planar (r.m.s. deviation = 0.535 Å), and coplanar with each other, forming a dihedral angle of 5.4 (1)°. Four weak inter­molecular hydrogen bonds (C—H⋯O and C—H⋯N) are observed in the structure, which join mol­ecules into a network parallel to (101).