Novel Nucleophilic 5-Substitution Route to 1,2,3-Thiadiazoles

New reactions of 4,5-disubstituted 1,2,3-thiadiazoles in the presence of NaH

“…[4][5][6] The yields of 2a-j were increased compared to the previously reported procedures by using a small excess of thionyl chloride in methylene chloride. 5-Benzylthio-4-phenyl-1,2,3-thiadiazole 2k was prepared according to an earlier reported procedure.…”

“…We now report that 4,5-disubstituted-1,2,3-thiadiazoles 2a-k containing an active methylene fragment are variously transformed in the presence of NaH into a 1,4-dithiafulvene 4, 1,2,3-thiadiazolylalkylketones 5a-c, 5-(2-aryl-1-phenylethenyl)-1,2,3-thiadiazole (11), 1,4-dialkyl-3,6-bis(phenylmethylidene)-2,5-dithiabicyclo[2.2.1]heptane 13a,b, bis-2,4-(1,2,3-thiadiazol-5-yl)-alkenes 12a-c and (6-benzyl-3,4-diphenyl-3,4-dihydro-2H-thiopyran-2-ylidene)(phenyl)-methanethiol 15 (Schemes 2, 3,4). …”

“…Thus, recently documented thermal transformations of 1-(1,2,3-thiadiazol-5-yl)-1H-1,2,3-benzotriazoles involving intramolecular heterocyclization lead to 3-R-4H- [1,2,3]thiadiazolo [3,4-a]benzimidazol-2-ium-4-ides. 4 Heating 4-aryl-and 4-heteroaryl-5-arylthioxy-1,2,3-thiadiazoles in the presence of sodium hydride in DMF forms two isomeric benzo-1,4-dithiines as a result of intramolecular recyclization or as a result of a dimerization process 5 (Scheme 1). …”

Thiadiazoles

“…In particular, different 5-substituted derivatives have been synthesized by Katritzky et al [63] following a procedure that exploits the chemistry of the benzotriazole system. Thus, the 1-(1,2,3-thiadiazol-5-yl)-1H-1,2,3-benzotriazole 94 has been transformed into 5-[(4-methylphenyl)thio]-1,2,3-thiadiazoles 96 (X ¼ S) and 5-phenoxy-4-phenyl-1,2,3-thiadiazoles 97 (X ¼ O).…”

Synthesis of substituted 2λ4δ2-[1,2,3]thiadiazolo[3,4-c]benzimidazoles and 2λ4δ2-[1,2,3,5]thiatriazolo[3,4-c]benzimidazoles

“…6,7 1,2,3-Thiadiazoles are also valuable as synthetic intermediates for substituted acetylenes, [8][9][10] thioamides, 11 5-aryloxy(thio)-1,2,3-thiadiazoles 12 and other heterocyclic systems. 13 We have reported previously the synthesis of the first representatives of a fused heterocyclic system containing the 1,2,3-thiadiazole moiety - [1,2,3]thiadiazolo [3,4-c]benzimidazole.…”