5- Alkylamino-1.2,4-thiadiazole

Hydrolysis of amino-alkylamino-l,2,5-thiadiazole 1-oxides 55 with concentrated aqueous HC1 gave the amidines 56 (Equation 4) <2001JME1231>. The hydrolysis reactions of 2-alkyl-4-amino-2,3-dihydro-l, 2,5-thiadiazol-3-one 1,1-dioxides 57 in the range 24-73 °C in buffered aqueous solutions gave the corresponding 2-amino-2-[(iV-alkyl-substituted-sulfamoyl)imino]acetic acid salts 58 (Equation 5) <1998JP0489>. 

Reactions of 1,2,4-thiadiazoles with radicals and electron deficient species are virtually unknown. Catalytic and dissolving metal reductions usually result in S—N bond cleavage. For example, the 5-anilino-3-hydroxy derivative (51) gives a good yield of l-phenyl-2-thiobiuret (52) on Zn-HCl reduction (Scheme 27). Reduction of the diamino derivative (53) gives amidinothiourea (54) from which it may be prepared by oxidation (Scheme 28). Under similar conditions, cleavage of the 3,5-diphenyl derivative (55) results in loss of sulfur and formation of benzylbenzamidine (56 Scheme 29). Reduction of 5-alkylamino-or 5-arylamino-3-alkylthio derivatives (57) with H2S in pyridine-triethylamine or sodium in liquid ammonia yields 1-substituted dithiobiurets (58 Scheme 30). 

Hydrolysis of amino-alkylamino-l,2,5-thiadiazole 1-oxides 240 with concentrated aqueous HCI gives the amidines 241 <2001JME1231>. 

By cyclizing thiosemicarbazide with iV,iV -diphenylcarbodiimide, Goodfrey and Kurzer obtained 2-amino-5-anilino-l,3,4-thiadiazole (57) with the thiocarbamidoaminoguanidine (56) as intermediate. 57 and similar compounds (59), also with alkylamino groups, have... 

Acylamino-l,3,4-thiadiazoles have been reduced with lithium aluminium hydride to the corresponding 2-alkylamino derivatives. 2-Amino-5-aryl-l,3,4-thiadiazoles have been found to undergo the Mannich reaction with a variety of methylene compounds. ... 

The formation of compounds 2 is rationalized by thermal elimination of sulfur.9 On the other hand, the formation of compounds 3 is unique and requires a more complex pathway, because two alkylamino groups arc introduced on the thiadiazole ring system.9... 

Alkylation reactions of 5-amino resin 55 with alkyl halides (R diversity element) provided the desired 3-substituted 5-(iV-alkylamino)-1,2,4-thiadiazole resin 56. In a similar manner, 3-substituted 5-(A-acylamino)-1,2,4-thiadiazole resin 57 was produced by acylation reactions of resins 55 with acid chlorides (R diversity element). More important, resins 56a (R = Ph, R = Bn) and 57a (R = R = Ph) underwent smooth... 

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