Pyridinium 5-[(1,3-diethyl-6-hydr-oxy-4-oxo-2-thioxo-1,2,3,4-tetra-hydro-pyrimidin-5-yl)(2-methoxy-phen-yl)meth-yl]-1,3-diethyl-4,6-dioxo-2-thioxopyrimidin-5-ide.

1,3-Diethyl-2-thio-barbituric acid reacts with 2-anisaldehyde to form the Michael addition product 2-anisylbis(1,3-diethyl-2-thio-barbitur-5-yl)methanate, which crystallizes as the title pyridin-ium salt, C(5)H(6)N(+)·C(24)H(29)N(4)O(5)S(2) (-), when it reacts with the pyridine used to catalyse the reaction. There are two independent ion pairs in the crystal structure. The anion features a methine C atom connected to three six-membered rings; one of the rings carries a hydr-oxy group, which engages in hydrogen bonding with the carbonyl group belonging to another ring. The monoclinic unit cell emulates an ortho-rhom-bic unit cell, and is a twin with a minor twin component of 35%.