Crystallographic Studies of Dehydration Phenomenon in Methyl 3-hydroxy-2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1λ 6-benzo[e][1,2]thiazine-3-carboxylate

Abstract

Methyl 3-hydroxy-2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1λ6-benzo[e][1,2]thiazine-3-carboxylate was synthesized in single step through in situ bromination of methyl 2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1λ6-benzo[e][1,2]thiazine-3-carboxylate using dibenzoyl peroxide & N-bromosuccinamide and was crystallized in acetone-ethyl acetate mixture (1:1). However, crystallization in methanol converted the title compound to methyl 3-methoxy-2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1λ6-benzo[e][1,2]thiazine-3-carboxylate, an unsymmetrical ether. The titled compound C11H11NO6S (3) crystallized in nonoclinic space group P21/c whereas, the compound C12H13NO6S (4) crystallized in triclinic space group P-1. X-ray studies shows that the molecules of 1 are linked into a one-dimensional framework structure by C–H···O and O–H···O hydrogen bonds, while in 4, intermolecular C–H···O and C–H···π hydrogen bonds and a π···π interaction result in the formation of infinite chains running along the [010] and [001] directions.