Cyclization of 2,4-dinitronaphth-1-yl amino acids and their analogues to naphthimindazol-N-oxides: Kinetics and mechanism

A variety of novel naphthimindazol-N-oxides and naphththiazol-N-oxide have been prepared in a simple two-step process. The first step involves the reaction of 1-chloro-2,4-dinitronaphthalene with glycine, alanine, glycolic acid, thioglycolic acid, and their methyl esters affording substitution products, the subsequent treatment of which with base furnishes naphthimindazol-N-oxide and naphththiazol-N-oxide derivatives. Stepwise reaction mechanisms via carbanions, nitrogen anions, and spiro Meisenheimer intermediates are proposed. The action of 10% NaOH in dioxane on the substitution products was measured spectrophotochemically, and the kinetic studies suggested that the N-naphthyl glycine and N-naphthyl alanine follow a second-order rate law while S-naphthyl thioglycolic acid is accurately first-order kinetics.