(5R/5S)-2,5-diphenyl-7-[trans-(1R/1S,2S/2R)-2-phenylcyclohexyloxy]-2,3,5,8-tetrahydro-1H-1,2,4-triazolo[1,2-a]pyridazine-1,3-dione-water (1/1): a face-selective Diels-Alder reaction of 2-alkoxy-1,3-butadiene

The title compound, C30H29N3O3 . H2O, is the final product in the Diels-Alder reaction between a 2-alkoxydiene and a reactive dienophile such as phenyltriazolinedione after recrystallization from methanol. The water molecule forms a hydrogen bond with a carbonyl O atom in one dione molecule and a weaker interaction with an N atom in a symmetry-related molecule, forming dimers linked by the water molecule. Atoms in the five-membered ring stemming from the dienophile molecule are related by a non-crystallographic C-2 axis through an N atom.