Diazonium salts alcohol synthesis

This method for the synthesis of purine nucleosides, developed by Todd and coworkers, was valuable in that it unequivocally established that the point of attachment of the sugar moiety of the nucleic acid nucleosides is at N-9. In this synthesis, a sugar is condensed with a 4,6-diaminopyrim-idine (132) in alcohol solution in the presence of acid, and the resultant 4-amino-6-(glycosylamino)pyrimidine (133) is coupled with an aromatic diazonium salt. The (phenylazo)pyrimidine (134) is reduced to the amino compound (135), and cyclization to the purine nucleoside (137) is accomplished by way of the 5-thioformamide compound (136). 

As part of their study aimed at the synthesis of veratramine (XXVI) Johnson and collaborators have synthesized alcohol XLIV and ketone XLV. The latter was synthesized by the same procedure as its dihydro derivative XXXI. XLIV was prepared by the following route. The oxime XXXV was first converted into the acetyl derivative XLVI which was transformed, by Beckman rearrangement with phosphorus oxychloride in pyridine, into the acetamido compound XLVII. Alkaline hydrolysis of the latter afforded the amino alcohol XLVIII which was converted by reduction of the diazonium salt with zinc and ethanol into the alcohol XLIV 28, 34). 

The synthesis of azoloannelated fluoro-l,2,4-triazines - 2-R-6-fluoro-1,2,4-triazolo[5,l-c][l,2,4]triazin-7(4H)-ones 10 has been recently described [16]. The coupling of l,2,4-triazolyl-5-diazonium salts 11 with ethyl 2-fluoroacetate and the accompanied deacetylation leads to the formation of hydrazones 12 followed by cyclization on heating in aqueous alcohol in the presence of sodium acetate into the target fluoro compounds 10 (Scheme 9). 

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