Enantioselective synthesis of C3-functionalized 2,1-benzothiazine 2,2-dioxides by N-heterocyclic carbene catalysis

We present herein an approach for the enantioselective C3-functionalization of 2,1-benzothiazine 2,2-dioxides using N-heterocyclic carbene (NHC) catalysis. Our method involves a sequence of [3+3] cycloaddition and ring-opening reactions with different N- and O-nucleophiles, followed by silylation. Overcoming the challenge of selectivity targeting the C3 position, this protocol demonstrates a broad substrate scope and high enantioselectivity. This marks a significant advancement in the field of NHC-catalyzed transformations.

Multifunctional aldose reductase inhibitors based on 2H-benzothiazine 1,1-dioxide

A series of benzothiazine derivatives were designed and synthesized for the development of drug candidates for diabetic complications.

2-[(E)-1,1-Dioxo-2-(2,4,5-tri-fluoro-benz-yl)-3,4-di-hydro-2H-1,2-benzo-thia-zin-4-yl-idene]acetic acid

In the asymmetric unit of the title compound, C17H12F3NO4S, there are two conformationally similar mol-ecules in which the heterocyclic thia-zine ring adopts a half-chair conformation, with the dihedral angle between the two benzene rings being 24.84 (8) and 37.42 (8)°. In the crystal, the mol-ecules form dimers through cyclic carb-oxy-lic acid O-H⋯O hydrogen-bonding associations [graph set R (2) 2(8)] and are extended into chains along [101] through weak C-H⋯Osulfin-yl hydrogen bonds [graph set R (2) 2(14)]..

2-[(Z)-1,1-Dioxo-2-(2,4,5-tri-fluoro-benz-yl)-3,4-di-hydro-2H-1,2-benzo-thia-zin-4-yl-idene]acetic acid

In the title compound, C17H12F3NO4S, the heterocyclic thia-zine ring adopts a half-chair conformation and the dihedral angle between the benzene rings is 43.28 (9)°. The α,β-unsaturated C=C group is inclined at an angle of 21.0 (3)° to the benzene ring of the benzo-thia-zine moiety. In the crystal, inversion dimers linked by pairs of carb-oxy-lic acid O-H⋯O hydrogen bonds generate R 2 (2)(8) loops. Each of the F atoms accepts a Ca-H⋯F (a = aromatic) hydrogen bond from an adjacent mol-ecule, resulting in (001) sheets.