Copper‐Catalyzed Cascade Acylation/Coupling Cyclization Process for the Synthesis of Polycyclic Fused Imidazo[2,1‐‐b][1,3]thiazinones

Abstract

A new and efficient cascade synthesis of polycyclic fused imidazo[2,1-b][1,3]thiazinones has been developed. This protocol includes an intermolecular N-acylation followed by a copper-catalyzed intramolecular C-S coupling reaction. The methodology is applied to a wide range of 2-iodo, 2-bromo, and 2-chloro benzoyl chlorides to yield the polycyclic fused imidazo[2,1-b][1,3]thiazinones in good to excellent yields.

Facile Access to Polycyclic Fused Azo[2,1‐b] [1,3]‐benzothiazinone via Iron‐Catalyzed Cascade Reaction

“…3‐Chloro‐12H‐benzimidazo[2,1‐b][1,3]benzothiazin‐12‐one ( 3e ). Green solid; mp 209–211°C; 1 H NMR (500 MHz, CDCl 3 /TMS): δ 8.59 (d, J = 7.5 Hz, 1H), 8.56 (d, J = 8.5 Hz, 1H), 7.77 (d, J = 8.0 Hz,1H), 7.57 (d, J = 2.0 Hz, 1H), 7.49–7.43 (m, 3H) ppm; 13 C NMR (125 MHz, CDCl 3 /TMS): δ 158.8, 145.4, 142.6, 140.8, 134.2, 132.7, 131.8, 127.8, 126.1, 125.4, 124.5, 121.2, 118.7, 116.0 ppm.…”

“…5H‐Imidazo[2,1‐b][1,3]benzothiazin‐5‐one ( 3g ). White solid; mp 190–192°C; 1 H NMR (500 MHz, CDCl 3 /TMS): δ 8.61 (dd, J = 8.0, 1.0 Hz, 1H), 8.07 (d, J = 1.5 Hz, 1H), 7.74–7.71 (m, 1H), 7.70 (d, J = 1.5 Hz, 1H), 7.60–7.52 (m, 1H), 7.38 (d, J = 1.5 Hz, 1H) ppm; 13 C NMR (125 MHz, CDCl 3 /TMS): δ 158.2, 139.7, 133.9, 133.7, 131.6, 131.4, 126.9, 126.1, 121.2, 115.5 ppm.…”

Chemistry of 1,3-thiazin-4-ones and their derivatives, 1995 - mid-2018

“…In a similar reaction, 2-halo-1-benzoyl chlorides 299 were converted in a cascade reaction to the b-fused imidazole/benzimidazole products 301/302 (Scheme 91). 161 The halogen could be Cl, Br, or I. 1,10-Phenanthroline 300 was used as a ligand.…”

“…2-Chloropyridine-3-carbonyl chloride 244 was converted in a cascade reaction to the triheterocyclic imidazole product 425 in high yield (Scheme 132). 161 1,10-Phenanthroline 300 was used as a ligand. The benzimidazole was also prepared.…”

Transition-metal-free synthesis of imidazobenzothiazines via domino C-S/C-N bond formation

“…In the synthesis of these compounds, tandem C-S/C-N formation shows obvious advances over other methods due to their facile one-pot procedure [34][35][36][37]. In addition, recent advances in tandem reactions with C-X (X=N, S, O) coupling reactions show their great importance in both methodology development [37][38][39][40][41][42] and natural product synthesis [43].…”