Occurrence of Ring Opening in the Reactions of Some 2,6-Disubstituted Purines with Potassium Amide in Liquid Ammonia

Article abstract of DOI:10.1021/jo00156a013

The reaction of 2,6-dichloropurine with potassium amide in liquid ammonia gives three products: 2-chloroadenine, 2,6-diaminopurine, and 4-cyano-5-(cyanoamino)imidazole.We have shown that 2-chloroadenine is formed first.This compound is converted into 4-cyano-5-(cyanoamino)imidazole, which finally gives 2,6-diaminopurine. 2,6-Diaminopurine can also be obtained by conversion of the 4-cyano-5-(cyanoamino)imidazole with methanolic ammonia, but the mechanism of this conversion is different from the one with potassium amide in liquid ammonia.To prove these mechanisms via 15N labeling we have shown that reductive deamination of 2,6-diamino-9-methylpurine with sodium in liquid ammonia removes the amino group at position 6 without ring opening.Reaction of 2-amino-6-chloropurine with potassium amide in liquid ammonia also gives 4-cyano-5-(cyanoamino)imidazole with some 2,6-diaminopurine.