Premium
Reaction of α,β‐unsaturated ketones with guanidine. Substituent effects on the protonation constants of 2‐amino‐4,6‐diarylpyrimidines
Author(s) -
AlHajjar Farouk H.,
Sabri Salim S.
Publication year - 1982
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570190521
Subject(s) - chemistry , substituent , protonation , guanidine , medicinal chemistry , sodium hydroxide , hydrochloride , hammett equation , stereochemistry , crystallography , computational chemistry , reaction rate constant , organic chemistry , kinetics , ion , physics , quantum mechanics
Abstract 1,3‐Diaryl‐2‐propen‐1‐ones, I, reacted with guanidine hydrochloride (II) in the presence of 3 moles of sodium hydroxide to give the corresponding 2‐amino‐4,6‐diarylpyrimidines, III. The structure and configuration of the products are based on chemical and spectroscopic evidence. The protonation constants of these compounds (series A and series B) have been determined in 50 volume percent ethanol‐water medium. Excellent linear correlations are obtained when p K a values of the two series of 2‐amino‐4,6‐diarylpyrimidines, IIIa‐j and IIIk‐r, are plotted against the substituent constant, σ x, and the polar substituent constant, σ * xC 6 H 4 , for substituted phenyl groups. The p K a values have also been correlated with the extended Hammett equation. The correlation follows the equations: Series A; p K a = 3.273 ‐ 0.820σI,X ‐ 0.662σR,X Series B; p K a = 3.169 ‐ 0.424σI,X ‐ 0.137σR,X