The chemistry of nitro-compounds. Part III. The intramolecular nucleophilic displacement of aromatic nitro-groups by carbanions

Abstract

Heating α-(N-methyl-N-o-nitrobenzoylamino)phenylacetonitrile (1a) with sodium ethoxide in ethanol affords moderate yields of 2-methyl-3-oxo-1-phenylisoindoline-1-carboxamide (3a) and benzoic acid. Similar treatment of the N-benzyl and N-phenyl o-nitrobenzamide derivatives (1b and c) yields, in addition to benzoic acid, separable mixtures of the 3-oxoisoindoline-1-carbonitriles (2b and c), the derived amides (3b and c), and the 3-phenyliso-indolin-1-ones (4b and c). Isoindolinone formation by direct intramolecular displacement of the ortho-nitro-group by the cyanobenzyl carbanion generated in the side-chain is indicated by the conversion of the amides (1a–c) in hot ethanolic sodium carbonate in high yield into the 3-oxoisoindoline-1-carbonitriles (2a–c). In addition to benzoic acid, the latter reactions respectively afford o-azidobenzoic acid (12), benzaldehyde o-carboxy-phenylhydrazone (13), and azobenzene-2-carboxylic acid (14) as by-products. The substituted benzamides (6), (7a and b), and (8a and b) are unaffected by ethanolic sodium carbonate. In contrast, the 2-nitro-5-methyl compound (6) and the 2-chloro-5-nitro-derivative (8c) are respectively converted by heating with ethanolic sodium ethoxide and ethanolic sodium carbonate into the 5-methyl- and 5-nitro-3-oxo-1,2-diphenylisoindoline-1-carbonitriles (9a and b). The mechanisms of the reactions are discussed.