title: 6-Methyl-sulfanyl-4H-pyrimido[1,6-a]pyrimidin-4-one.
abstract: Reaction of 2-(methyl-sulfan-yl)pyrimidin-4-amine with the 5-(methoxy-vinyl-idene) derivative of Meldrum's acid and subsequent heating of the product in Dowtherm fluid yielded the title compound, C(8)H(7)N(3)OS, which was proven to contain a bicyclic 4H-pyrimido[1,6-a]pyrimidine system. All non-H atoms of the mol-ecule are coplanar within 0.15 Å. The bond-length distribution in the bicyclic core shows localization of the double bonds. The geometry of the intra-molecular S⋯O 1,5-contact [2.534 (2) Å] is consistent with the existence of an attractive inter-action.
authors.forename: Quinhua
authors.initials: Q
authors.lastname: Huang
authors.forename: Paul F
authors.initials: PF
authors.lastname: Richardson
authors.forename: Eugene
authors.initials: E
authors.lastname: Rui
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.forename: Alex
authors.initials: A
authors.lastname: Yanovsky