Microwave Induced Synthesis of 3‐Aryl‐6‐(6‐/8‐substituted 4‐chloroquinoline‐3‐yl) ‐ s ‐triazolo [3,4‐b] −1,3,4‐thiadiazoles

The condensation of 4‐amino‐3‐aryl‐5‐mercapto‐1, 2, 4‐triazoles (1a‐f) with 6‐/8‐substituted 1,4‐dihydro‐4‐oxo‐quinoline‐3‐carboxylic adds (2a‐d) in the presence of phosphorus oxychloride on refluxng or under microwave irradiation gave twenty four novel 3‐aryl‐6‐ (6‐/8‐substituted 4‐chloroquinoline‐3‐yl)‐s‐triazolo[3,4‐b]‐1, 3,4‐thiadiazoles (4a‐x), Considerable increase in the reaction rate has been observed with improved yields under microwave irradiation. The structures of the compounds synthesized were determined by elemental analyses, IR, ¹H NMR and MS spectra. Their spectral properties and the reaction mechanism were also discussed. The preliminary biological test showed that some of compounds bad moderate antibacterial activities.     

One‐Pot Synthesis of 2‐Substituted 4‐Aryl‐4,5‐dihydro‐3,1‐benzoxazepines from 2‐(2‐Aminophenyl)‐1‐arylethanols via Dehydration of the Corresponding Amides

An efficient method for the preparation of 2‐substituted 4‐aryl‐4,5‐dihydro‐3,1‐benzoxazepine derivatives under mild conditions has been developed. The reaction of 2‐(2‐aminophenyl)ethanols 1 with acid chlorides in the presence of excess Et₃N in THF at room temperature gave the corresponding N‐acylated intermediates 2 , which were dehydrated by treatment with POCl₃ to give 2‐substituted 4‐aryl‐4,5‐dihydro‐3,1‐benzoxazepines 3 in a one‐pot reaction.     

Three‐Step Synthesis of 3‐Aryl‐2‐sulfanylthieno[2,3‐b]‐, ‐[2,3‐c]‐, or ‐[3,2‐c]pyridines from the Corresponding Aryl(halopyridinyl)methanones

A convenient three‐step procedure for the synthesis of three types of 3‐aryl‐2‐sulfanylthienopyridines 4, 8 , and 12 has been developed. The first step of the synthesis of thieno[2,3‐b]pyridine derivatives 4 is the replacement of the halo with a (sulfanylmethyl)sulfanyl group in aryl(2‐halopyridin‐3‐yl)methanones 1 by successive treatment with Na₂S?9 H₂O and chloromethyl sulfides to give aryl{2‐[(sulfanylmethyl)sulfanyl]pyridin‐3‐yl}methanones 2 . In the second step, these were treated with LDA (LiNⁱPr₂) to give 3‐aryl‐2,3‐dihydro‐2‐sulfanylthieno[2,3‐b]pyridin‐3‐ols 3 , which were dehydrated in the last step with SOCl₂ in the presence of pyridine to give the desired products. Similarly, thieno[2,3‐c]pyridine and thieno[3,2‐c]pyridine derivatives, 8 and 12 , respectively, can be prepared from aryl(3‐chloropyridin‐4‐yl)methanones 5 and aryl(4‐chloropyridin‐3‐yl)methanones 9 , respectively.     

A Convenient Synthesis of 2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]‐, ‐[2,3‐c]‐, or ‐[3,2‐c]pyridin‐4‐ones by the Reaction of the Corresponding 1‐(Chloropyridinyl)alk‐2‐en‐1‐ones with NaSH

2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]pyridin‐4‐ones 4 were prepared by a three‐step sequence from commercially available 2‐chloropyridine ( 1 ). Thus, successive treatment of 1 with ⁱPr₂NLi (LDA) and α,β‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2 , which were oxidized with MnO₂ to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3 . The reactions of 3 with NaSH?n H₂O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4H‐thiopyrano[2,3‐c]pyridin‐4‐ones 8 and 2,3‐dihydro‐4H‐thiopyrano[3,2‐c]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine ( 5 ) and 4‐chloropyridine ( 9 ), respectively.