Novel One-Pot Microwave Assisted Gewald Synthesis of 2-Acyl Amino Thiophenes on Solid Support

Abstract

A new efficient variation of the Gewald reaction is described. A number of tetrasubstituted 2-acyl aminothiophenes have been prepared via a one-pot microwave assisted Gewald reaction on solid support. This reaction proceeds in good yields within only a few hours rendering diverse products in a time-effective manner. The scope and limitations of the reaction have been investigated.

The Reaction of Cyanoacetylhydrazine with Chloroacetone: Synthesis of 1,2,4-Triazine, 1,3,4-Oxadiazine and Their Fused Derivatives with Antitumor Activities

“…On the other hand, the reaction of compound 3 with potassium cyanide (14) gave the 3-amino pyrazole derivative 15. Formation of the pyrazole derivative 15 took place in analogous with our recent reported work [18].…”

“…236˚C -240˚C. Calculated for C 18 7-Methyl-9-phenyl-8,9-dihydro-1,5,6,8a,9-pentaazafluorene-2,4-diamine (11a) and 4-Amino-7-methyl-9-phenyl-8,9-dihydro-1,5,6,8a,9-pentaaza-fluoren-2-ol (11b).…”

Heterocyclic Chemistry Using Microwave‐Assisted Approaches

“…It is interesting to note that fixed microwave power input provided improved yields over constant temperature conditions (variable microwave power input). This chemistry was successfully extended to a solid-phase format (Rink amide resin) 10 An interesting modification of the Gewald thiophene synthesis combined a onepot, multi-component coupling on solid-phase, with microwave-assisted synthesis 12 . Cyanoacetic acid bound Wang resin was treated with elemental sulphur and a range of aldehydes or ketones under microwave heating (see Chapter 5, Section 5.2.5).…”

A facile and environmentally benign polyethylene glycol 600-mediated method for the synthesis of densely functionalized 2-aminothiophene derivatives under ultrasonication

“…For example, some basic compounds such as imidazole (28), Mg/La mixed oxide (29), silica-supported piperazine (30), bovine serum albumin (31), ZnO nano-particles (32), saturated NaHCO 3 solution in PEG 600 (13) and ionic liquids can be mentioned (33). Furthermore, techniques such as solid phase synthesis (34), microwave irradiation combined with insoluble polymer support (35) or soluble polymer support (36), and electrochemical activation (37) have also been reported. In spite of their merits, most of these methods require the use of basic compounds, high catalyst loading, long reaction times and expensive catalysts or toxic solvents.…”