Solvent‐Free Pot‐, Atom‐ and Step‐Economic Synthesis of Novel Benzo[d]thiazole‐[1,3]‐thiazine Hybrids in a One‐Pot Reaction

Abstract

The first catalyst-and solvent-free synthesis of novel benzo[d]thiazole-[1,3]-thiazine hybridsf rom benzo[d]thiazol-2-amines, isothiocyanates and dialkyl acetylenedicarboxylates with no more than 30 min of microwave irradiation is described. Moreover,t he proposed strategy involves neither tedious workup nor column purification steps. This approachp rovides ad iversity-oriented route for the rapid assembly of benzo[d]thiazole-[1,3]-thiazine frameworks. Furthermore, the methodology has excellent green credentials, scoring welli nanumber of green metrics, hence showing this approach to be an ideal green and sustainable process.

An Efficient Combinatorial Synthesis of Novel Thiazolidinone‐Bis Schiff Base Hybrids Using One‐Pot Multicomponent Reaction

“…Based on the existing literature, [13] two mechanistic pathways for the reaction are suggested (Scheme 4). The proposed pathway 1 involves the reaction of hydrazine 2 with isothiocyanate 1 leading to the formation of the thiosemicarbazide intermediate I ; whereas pathway 2 starts with the reaction of hydrazine with aldehyde 3 to form the hydrazone intermediate I′ .…”

“…As a part of our ongoing endeavors in developing green synthetic methods to achieve biologically important molecular scaffolds, [12,13] we report herein an efficient synthesis of thiazolidinone‐bis Schiff base hybrids 5 by the four‐component reaction of isothiocyanate 1 (1 equiv. ), hydrazine 2 (1 equiv.…”

α-Aminoazoles/azines: key reaction partners for multicomponent reactions

“…Next, P. Wadhwa's group developed a catalyst- and solvent-free approach for the diversity-oriented synthesis of thiazole linked thiazin derivatives 377 from the three-component reaction of 2-aminobenzothiazoles 3b, various isothiocyanates 376 and DAAD 362 irradiated under microwave heating at 120 °C for 30 min. 223 Conversely, when the same combination of reactants was heated in the conventional way, the products were formed after 10 h with low yields. With microwave heating, the quality of their approach was enhanced greatly both in terms of reaction time and product yield.…”

Thia‐Michael Addition: An Emerging Strategy in Organic Synthesis

“…As ac ontinuation of our interest in the synthesis of new hybrid molecules,w er eported ad omino procedure to access functionalized benzo[d]thiazole-[1,3]-thiazine hybrids (111)i n an efficient manner.T his methode mployed benzo[d]-thiazol-2amines 110,i sothiocyanates 14,a nd dialkyla cetylenedicarboxylates 33 and proceeded very well under microwave irradiation at 120 8Cf or 20 min under solventa nd catalyst-free conditions (Scheme83). [122] The three-componentd omino reactioni nvolved as equential nucleophilic-addition/thia-Michael-addi-tion/intramolecular-cyclization sequence and tolerated several different functional groups on the benzo[d]-thiazol-2-amine (110), includinge thoxy,m ethyl, chloro, and fluoro groups, to afford the corresponding benzo[d]thiazole- [1,3]-thiazine hybrids (111)i ng ood yields. In addition, the reaction worked well with 2-aminothiazole, although it was unsuccessful with 2-aminothiazoline.…”