Microwave Assisted Synthesis and Unusual Coupling of Some Novel Pyrido[3,2-f][1,4]thiazepines

Abstract

3-Amino-3-thioxopropanamide (1) reacted with ethyl acetoacetate to form 6-hydroxy-4-methyl-2-thioxo-2,3-dihydropyridine-3-carboxamide (2), which reacted with α-haloketones 3 to produce 2,3-disubstituted-8-hydroxy-6-methyl-2H,5H-pyrido[3,2-f]-[1,4]thiazepin-5-ones 4a-c. Benzoylation of 4c led to the formation of the dibenzoate derivative 9. Compounds 4a-c could be prepared stepwise through the formation of S-alkylated derivatives 10a-c. Compounds 2, 4a-c, 9 and 10a-c were prepared using microwave as a source of heat, and gave better yields in shorter times than those achieved by traditional methods. Coupling of 4a-c with arenediazonium chlorides proceeded unusually to give the 6-hydroxy-4-methyl-2-(arylazo)thieno[2,3-b]pyridin-3(2H)-one ring contraction products 14. Structures of the newly synthesized compounds were proven by spectral and chemical methods.

Microwave Assisted Synthesis of Some New Thiazolopyrimidine, Thiazolodipyrimidine and Thiazolopyrimidothiazolopyrimidine Derivatives with Potential Antioxidant and Antimicrobial Activity

“…Our research group has recently [ 22 , 23 , 24 , 25 ] been interested in performing synthesis of some heterocyclic compounds under environmentally friendly, time saving microwave-assisted conditions. Accordingly, we re-synthesized the previously described compounds 1a – d , 3a – d , 5a – d , and 7a – c under microwave conditions, aiming to increase reaction yields and reduce the reaction times.…”

Bromination and Diazo-Coupling of Pyridinethiones; Microwave Assisted Synthesis of Isothiazolopyridine, Pyridothiazine and Pyridothiazepines

“…The starting compound 6-hydroxy-4-methyl-2-thioxo-2,3-dihydropyridine-3-carboxamide ( 2 ) was prepared from 3-amino-3-thioxopropanamide [monothiomalonamide, ( 1 )] [ 16 ] and ethyl acetoacetate according to the literature procedure [ 17 ] ( Scheme 1 ). Bromination of 2 with bromine in acetic acid yielded 3-bromo-6-hydroxy-4-methyl-2-thioxo-2,3-dihydropyridine-3-carboxamide ( 3 ).…”

“…Our research group has recently [ 17 , 18 , 19 ] been interested in performing synthesis of some heterocyclic compounds under environmentally friendly, time saving microwave-assisted conditions. Accordingly, we re-synthesized the previously described compounds 8 , 10 , 11a , b , 12 and 13 under microwave conditions, aiming to increase reaction yields and reduce the reaction times.…”

“…The temperature of the reaction mixture was monitored using a calibrated infrared temperature control under the reaction vessel, and control of the pressure was performed with a pressure sensor connected to the septum of the vessel. 3-Amino-3-thioxopropanamide [monothiomalonamide ( 1 )] and 6-hydroxy-4-methyl-2-thioxo-2,3-dihydropyridine-3-carboxamide ( 2 ) were prepared according to literature procedures [ 16 , 17 ]. Reported 1 H-NMR and 13 C-NMR of 2 [ 14 ] are given for comparison: 1 H-NMR: 2.30 (s, 3H, CH 3 ), 3.85 (br s, 1H, OH, D 2 O exchangeable), 5.24 (s, 1H, H-3), 6.10 (s, 1H, H-5), 7.40 (br s, 2H, NH 2 , D 2 O exchangeable); 13 C-NMR: 20.3 (CH 3 ), 71.5 (C-3), 112.1 (C-5), 137.3, 162.3 (sp2 C), 173.1 (CO), 188.0 (CS).…”

Synthesis and Antibacterial Evaluation of Novel Heterocyclic Compounds Containing a Sulfonamido Moiety

“…Heterocyclic sulfonamides are used as carbonic anhydrase inhibitors [ 1 , 2 , 3 ], antibacterial agents [ 4 ], anticancer, anti-inflammatory and analgesic agents [ 5 ], β3-adrenergic receptor agonists [ 6 ], PC-1 inhibitors [ 7 ], antifungal agents [ 8 ] and antiviral agents [ 9 ]. For these vast biological activities and in continuation of our work [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] on the synthesis of novel heterocyclic systems exhibiting biological activity, we undertook the synthesis of a new series of compounds incorporating the abovementioned biologically active moieties in one molecule.…”