Search results for "Diketene"
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Preparation of 5-methyl-2-sulfanyl-7h-1,3,4-thiadiazolo[3,2-a]-pyrimidin-7-ones
2007
7H-1,3,4-Thiadiazolo[3,2-a]pyrimidin-7-ones can be prepared by the acylation of 5-amino-1,3,4-thiadiazoles with diketene and subsequent ring closure (dehydration). Whereas arylthio substituents (SC6H5) can be introduced in 2-position by the replacement of Br, alkylthio groups (SC2H5) have to be already presentin the starting 5-amino-1,3,4-thiadiazole. The ambident nucleophile 2-thiazolidinethione reacts in the Br substitution reaction on the N atom.
Preparation of 2-amino-5-methyl-7H-1,3,4-thiadiazolo[3,2-α]pyrimidin-7-ones
2005
2-Amino substituted 7H-1,3,4-thiadiazolo[3,2-α]pyrimidin-7-ones 11a-e were prepared by the reaction of 2-bromo-5-amino-1,3,4-thiadiazole (1b) and diketene (8), subsequent cyclocondensation (9b 3b) and displacement of the bromo substituents by the reaction with primary or secondary amines (3b 11a-e). The hydrogen atom 6-H in the heterobicycle 3b is replaced by a Cl or Br atom in the transformation of 3b 14a,b. The 2-bromo-6-chloro compound 14a reacts chemoselectively in the 2-position with dimethylamine (14a 15). The structure elucidations are based on one- and two-dimensional NMR techniques including a heteronuclear NOE measurement.