RING-CHAIN TAUTOMERISM - PART 9 - 2-ACYLBENZAMIDES, 8-ACYL-1-NAPHTHAMIDES AND 5-ACYL-4-PHENANTHRAMIDES

Ring-chain tautomerism in N-methyl- and N-(substituted phenyl)-2-formy lbenzamides, 2-benzoylbenzamides, 8-formyl-1-naphthamides, 8-benzoyl-1 -naphthamides and 5-formyl-4-phenanthramides has been investigated by IR and H-1 NMR spectroscopy and the measurement of their pK(a) values in 30% (v/v) dimethyl sulfoxide-water. The tautomeric pair synthesised , i.e. hydroxylactam-acylamide or aminolactone-iminocarboxylic acid, a ppears to be a function of the method of preparation and/or the basici ty of amine used. The cyclic tautomer, i.e. hydroxylactam or aminolact one, is predominant in all cases studied, However, equilibrium constan ts have been estimated from the pK(a) values for aminolactone-iminocar boxylic acid tautomerisation in which the effect of the links follow s imilar trends as found for the corresponding hydroxylactone-acylcarbox ylic acid tautomeric systems.