Studies on Azaindolizine Compounds. XVIII. Proton Magnetic Resonance Spectra of s-Triazolo-[1, 5-α] pyrimidine and its Derivatives.

Abstract

Proton magnetic resonance spectra of the s-triazolo [1, 5-α] pyrimidine derivatives are recorded to give the positional order of H6>H2>H5>H7 for the ring proton chemical shifts in τ-value. The methyl substituent effect on the proton chemical shifts and the correlation between the proton chemical shift and the local π-electron density on the carbon atom to which the proton is bonded, are discussed. Thus the charge densities determined from proton chemical shifts show a remarkably good correspondence with the charge distributions calculated by the simple Huckel MO method.