2-Methyl-4-oxo-6,7,8,9-tetrahydro-thieno[2',3':4,5]pyrimidino-[1,2-a]pyridine-3-carboxylic acid.

There are two independent mol-ecules in the asymmetric unit of the title compound, C(12)H(12)N(2)O(3)S. With the exception of the methyl-ene groups, a mean plane fitted through all non-H atoms of each mol-ecule has an r.m.

9-Furfuryl-idene-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-dimethyl-thieno[2',3':4,5]pyrimidino[1,2-a]pyridin-4-one with furfural in the presence of sodium hydroxide. One of the methyl-ene groups of the tetra-hydro-pyrido ring is disordered over two positions in a 0.87 (1):0.