Crystal structure of 3-meth-oxy-carbonyl-2-(4-meth-oxy-phen-yl)-8-oxo-1-aza-spiro[4.5]deca-1,6,9-trien-1-ium-1-olate.

The title compound, C18H17NO5, was prepared by a synthetic strategy based on the Heck reaction from Morita-Baylis-Hillman adducts. The five-membered ring adopts a slightly twisted conformation on the Ca-Cm (a = aromatic and m = methyl-ene) bond. The dihedral angle between the five-membered ring and the spiro aromatic ring is 89.35 (7)°; that between the five-membered ring and the 4-meth-oxy-benzene ring is 4.65 (7)°. Two short intra-molecular C-H⋯O contacts occur. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds to generate a three-dimensional network.