Efficient conversion of 6-cyanopurines into 6-alkoxyformimidoylpurines.
An extremely simple method for the selective synthesis of 9-aryl and 9-alkyl 6-alkoxy or 6-alkoxyformimidoylpurines from the corresponding 6-cyanopurines is described. The reaction is carried out with methanol or ethanol in the presence of DBU. At room temperature, nucleophilic attack by the primary alcohol occurs selectively on the cyano carbon atom, leading to 6-alkoxyformimidoylpurines in good yields. Heating the reaction mixture at a temperature greater than or equal to 78 degrees C leads to nucleophilic substitution of the substituent in the 6-position by the alkoxy group, generating the corresponding 6-alkoxypurines, also in excellent yields. The 6-alkoxyformimidoylpurines were used as intermediates in the synthesis of 6-carboxamidinopurines by reaction with methylamine (for 9-methylpurine 5a) or methyl ammonium chloride (for 9-arylpurines and 5b and 5c).
Carvalho
M Alice
MA
Departamento de Química, Universidade do Minho, Campus de Gualtar, 4710 Braga, Portugal.
Esteves
Teresa M
TM
Proença
M Fernanda
MF
Booth
Brian L
BL
D015394:Molecular Structure; D011687:Purines / Q000138:chemical synthesis* / Q000737:chemistry*
D011687:Purines; C018030:6-cyanopurine