Thiosemicarbazones 2-imino

Type D synthesis, where the 3,4-CN bond is being formed, involves the reaction of thiosemicarbazones of aldehydes, ketones, and esters 97 with 3,3-pentamethyleneoxaziridine 98 to afford 5-imino-3,3-pentamethylene-l,2,4-thiadi-azolidines 99 (Equation 27). yV-Acylthioureas also undergo this transformation but, whereas this reaction is fairly general for thiosemicarbazones, only acetyl and benzoyl thioureas give 1,2,4-thiadiazolidines <1996CHEC-II(4)307>. There have been no new reports of type D syntheses since the publication of CHEC-II(1996). 

Ferric chloride 2-Amino-l,3,4-tbiadiazoles from 2-imino-zl -1,3,4-thiadiazolines from thiosemicarbazones... 

Potassium hexacyanof errate(III)lsodium hydroxide 2-Imino-J -1,3,4-tbiadiazolines from thiosemicarbazones s. 19, 705... 

The product obtained from phenylthiosemicarbazide (92 R = H) and phosgene, described as 2-amino-4-phenyl-l,3,4-thiadiazolin-5-one (93 R = H), is in fact a mixture. Conditions have now been specified for the successful preparation of this compound (93 R = H) by this route. Oxidation of thiosemicarbazones. The oxidative cyclization of benzalthio-semicarbazones and of acetone thiocarbohydrazone is a well-known route to the 1,3,4-thiadiazole ring system. 4-Arylthiosemicarbazones of ketones (99) have now been shown to cyclize in this manner on being stirred in benzene in contact with suspended manganese dioxide, giving satisfactory yields of 5-imino-A -l,3,4-thiadiazolines (101). Ring-closure over alumina in chloroform slowly yields the isomeric l,2,4-triazoline-5-thiones (100). Bicyclo[3,3,l]non-2-en-9-one 4-phenylthiosemicarbazone... 

Monosubstituted thioureas give, in this reaction, a mixture of the isomeric 2-imino-4-thiazolidinones (196) and (197), the former predominating. Similarly, dithiocarbamates, thiocarbamates, thiosemicarbazides, and thiosemicarbazones give analogous 4-thiazolidinones of type (198) and (199), which were further studied. ... 

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