Practical and scalable access to halogenated 1,4-thiazines through a domino Morin-rearrangement/halogenation of N,S-acetals and their arylation based on Suzuki–Miyaura coupling

Abstract

1,4-Thiazine frameworks bearing a halide X (X = I, Br or Cl) at the α-position of their sulfur atom were prepared in one or two steps. This approach involves Morin-rearrangement of N,S-acetal using user-friendly N-halogenating reagents (NIS, NBS, NCS, DBH, DIH) or ICl to yield 1,4-thiazines. The latter successfully afforded the corresponding halogenated derivatives through interesting domino Morin-rearrangement/halogenation when an excess of halogenating agents, which act as catalysts and halogenating reagents in the same operation, was used. The brominated 1,4-thiazines, obtained in good to excellent yields, were then arylated through Pd(0)-catalyzed Suzuki–Miyaura coupling with organoboronic acids or esters. Ultimately, these conditions were applied to one example of an amidation reaction.