3H-1,2,3,4,6-penta-azaindenes (“8-azapurines.”) Part I. Covalent hydration, syntheses, and reductions

Abstract

Ionisation constants and ultraviolet spectra show that several 8-azapurines undergo covalent hydration in water, including the cations of 8-azapurine, 2-methyl- and 2-amino-8-azapurine, and the neutral species of 2-hydroxy- and 2-mercapto-8-azapurine. The ready oxidation of the hydrated form to 6-hydroxy-derivatives indicates that hydration produces 1,6-dihydro-6-hydroxy-8-azapurines. Four examples are given in which the insertion of a methyl group in the 6-position prevents this hydration.

Several new 8-azapurines are reported. The reduction of 8-azapurines is described for the first time, and the products are characterised as 1,6-dihydro-derivatives (i.e., 6,7-dihydro-3H-1,2,3,4,6-penta-azaindenes).