Copper-catalyzed aminothiolation of terminal alkynes with tunable regioselectivity

Abstract

A simple, mild, and efficient catalytic aminothiolation of terminal alkynes for the synthesis of both 2- and 3-substituted thiazolo[3,2-a]benzimidazoles is established upon catalysis with copper(i), in which complementary regioselectivities could be achieved by using sterically different phenanthroline-based ligands.

Unequivocal synthesis of substituted thiazolo[3,2-a]benzimidazoles

“…6 It is probable that the reports of single products are the result of selective isolation of one isomer, and not of selective synthesis. Several new approaches to the synthesis of thiazolo [3,2-a]benzimidazoles have been reported in recent years, [12][13][14][15][16][17][18][19] but unfortunately, none of them provides a general route to individual substituted isomers. Therefore, a search for alternative routes that could result in unequivocal formation of individual isomers was initiated.…”

“…1 H NMR [(CD3)2SO]: H 12.21 (br, 1H, NH), 7.58 (d, J 8.5 Hz, 1H, H-7), 7.54 (dd, J 8.6, 1.2 Hz, 1H, H-6), 7.41 (br s, 1H, H-4), 4.76 (t, J 5.4 Hz, 1H, CHO2), 4.37 (t, J 5.4 Hz, 2H, CH2N), 3.30 (s, 6H, 2 x CH3O). 13 A solution of 5 (0.306 g, 1 mmol) in a mixture of water (5 g) and conc. H2SO4 (45 g) was heated at 100 °C for 30 min and poured into ice-water.…”

Visible light-promoted intermolecular cyclization/aromatization of chalcones and 2-mercaptobenzimidazolesviaan EDA complex and a mechanism study

“…Traditionally, imidazo[2,1- b ]thiazoles were generated via copper-catalyzed intermolecular cyclization of 2-mercaptobenzimidazoles with pre-functionalized arenes, 13 pre-functionalized alkenes, 14 and alkynes. 15 Moreover, partially pre-functionalized arenes, such as ortho -dihalogenated arenes with electron-withdrawing groups, could also be used in base-promoted high-temperature reactions. 13 a The cyclization between ketones and 2-mercaptobenzimidazoles constructed imidazo[2,1- b ]thiazoles in a strong acid and DMSO/H 2 O 2 oxidation system.…”

Selective Thiocyanation and Aromatic Amination To Achieve Organized Annulation of Enaminone with Thiocyanate

“…However, the conventional methods for synthesizing this heterocycle are mainly based on the annulation of 2-mercaptoimidazole with ketones or prefunctionalized alkynes, which show deficiencies such as complex processes, harsh conditions, and narrow scope. Thus, many efforts have been made to achieve the annulation of 2-mercaptoimidazole with simple alkynes or alkenes (Scheme a). Recently, metal-free reactions such as peroxide or visible light have promoted aminothiolation of 2-mercaptoimidazole with ketone, and α-bromo­cinnamaldehydes have also been developed to achieve highly efficient construction of benzo­[4,5]­imidazo­[2,1- b ]­thiazoles.…”