Affoué Lucie Bédé^1,, Soleymane Koné¹, Mawa Koné¹, Amon Benjamine Assoma¹, Kicho Denis Yapo¹, Boka Robert N’Guessan¹, El Hadji Sawaliho Bamba¹, Thomas Yao N’Guessan¹

Experimental work has shown the possibility of cycloreversion of these heterocycles. In the case of 4H-1,3-thiazines, the possibilities of cycloreversion depend essentially on the nature of the substituent at the 4-position of the thiazine ring. Indeed, this reaction seems to be impossible with the methyl group in the 4-position but it is facilitated when the ethyl carboxylate group is at the same position. This difficulty does not occur with the selenium analogues. The density functional theory method at the level B3LYP/6-31G (d, p) was used to determine the influence of the heteroatom at position 1 on the cycloreversion reaction of these heterocycles. The thermodynamic and geometric parameters and the prediction of the reaction mechanism were developed in this work. The obtained results indicate a greater stability of the methylated thiazines in position 4. This would explain a difficulty of cycloreversion from these. These results also show a correlation between the reactivity of these heterocycles and their dipole moment.

cycloreversion, activation energy (Ea), Intrinsic Reaction Coordinate (IRC), 4H-1 3-thiazines, 4H-1 3-selenium