Methyl Rearrangement of Methoxy-Triazines in the Solid- and Liquid-State

2,4,6-Trimethoxy-1,3,5-triazine 11, and 6-methoxy-3,5-dimethyl-tetrahydrotriazine-2,4-dione 13 undergo intermolecular O→N methyl rearrangement in the liquid-state to 1,3,5-trimethyl 2,4,6-trioxohexahydro-s-triazine 14. 4,6-Dimethoxy-3-methyl-dihydro-triazine-2-one 12 was found to exhibit a different thermal behavior, and the methyl rearrangement takes place in the solid-state. The thermal behavior of each was investigated by calorimetry and high-temperature X-ray diffraction. It was found that 11 undergo phase transition to 11′, and the methyl rearrangement takes place in the melt. The solid-state methyl rearrangement of 12 is topochemically controlled. Two courses of methyl migration in the solid-state of 12 are proposed. A quantitative analysis of samples of 12 heated to different temperatures proves the existence of the two courses. A computer simulation was used to rationalize the reaction routes in 12 and 13.