Pyrimidine, reaction with

Chloro, 3-bromo, 3-iodo, and 3-nitro derivatives of 5,7-dimethyl-pyrazolo[l,5-a]pyrimidine derivatives were prepared by chlorination, bromination, iodination, and nitration of 3-unsubstituted 5,7-dimethyl-pyrazolo[l,5-a]pyrimidines. Reaction with bromine and potassium thiocyanate gave a 3-thiocyanato derivative, which was converted into the mercapto derivative upon saponification. Nitrosation gives the 3-nitroso derivative and acylation with trifluoroacetic anhydride affords the trifluoroacetyl derivative (74JMC645 77JMC386). 

Pyrimidines, reactions with nucleophilic reagents 90UK888. 

Pyrimidines. The pyrimidines react readily with hydroxyl radicals. Subsequent reactions of the pyrimidine-OH radical with oxygen lead to base destruction, thus G(-base) = G(OH) (6). Although the rate constants for pyrimidine reactions with Cl2 radicals are all one-twenty fifth or less of those of the OH radical rate constants (see Table I), they are still sufficiently high to ensure complete scavenging of Cl2" radicals by the pyrimidines at the concentrations used (2 X 10 4M) in steady state radiolysis. 

The direct formation of dipyrimidin-5-yl sulfides occurs on treatment of appropriate 5-unsubstituted pyrimidine substrates with sulfur mono- or di-chloride. Thus, reaction of uracil (83 R = H) with sulfur monochloride in boiling formic acid gives diuracil-5-yl sulfide in good yield sulfur dichloride gives a poor yield. Simple derivatives of uracil and barbituric acid undergo similar reactions but not cytosine, isocytosine, 2,4-bismethylthiopyrimidine or pyrimidine-4,6-dione (59). The mechanism is unknown (72AJC2275). 

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