5-Dimethylamino-3-Phenyl 4-Thiadiazole

The last example for the synthesis of this ring system discussed in this section is somewhat different from the previous ones as it presents formation of a positively charged thiadiazolo[3,2-tf][l,3,5]triazinium salt as published by Okide 1994JHC535 the 2 amino 5 alkyl[l,3,4]thiadiazole 167 was reacted with l chloro l,3 bis(dimethylamino) 3-phenyl-2-azaprop-2-enylium perchlorate (a reagent which was synthesized by the same author earlier <1992JHC1551>) to give the quaternary salt 168 in moderate yield (45%) (Scheme 32). 

Acetamide replaces a halogen atom (in 166, B = Ph) by the ace-tamido group (50-60% yield), while dimethylformamide yields 5-dimethylamino-3-phenyl-1,2,4-thiadiazole quantitatively.188... 

Acetylation of 5-amino-3-dimethylamino-l,2,4-thiadiazole yields the expected 5-acety-lamino derivative but no product was obtained when sulfonylation was attempted. 3-Amino-5-phenyl-l,2,4-thiadiazole (15 R = Ph) forms the expected derivatives (138), (139) and... 

As a rule, oxadiazoles and thiadiazoles are not nitrated. Reports on the production of 2-nitro-5-amino-l,3,4-thiadiazole during the nitration of 2-amino-l,3,4-thiadiaz-ole [274] proved erroneous [275], The compound obtained in this case was 2-nit-ramino-l,3,4-thiadiazole [275], There is only a single paper on the nitration of derivatives of 1,3,4-oxa- and 1,3,4-thiadiazoles [276], 2-Dimethylamino-l,3,4-oxa-and 2-dimethylamino-l,3,4-thiadiazoles react with the nitrating mixture with the formation of 2-dimethylamino-5-nitro derivatives. Aryl-substituted oxadiazoles and thiadiazoles are nitrated in the phenyl ring [277, 278],... 

Flash-vacuum pyrolysis at 550 °C/0.08 Torr of 2-(dimethylamino)-5-phenyl-6//-l,3,4-thiadi-azin-6-ones results in thermal fragmentation with formation of the corresponding N,N-dimethyl-5-phenyl-l,3,4-thiadiazol-2-amine together with dimethylcyanamide and benzo-nitrile.92... 

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