Naphthoquinone series

Summary

The condensation of 2 : 3-dichloro-l : 4-naphthoquinore (I) with compounds containing a reactive metnylene group in pyridine was studied. The reaction of (I) with ethyl acetoacetate in pyridine gave l-keto-2-carboethoxy-methylenyl-1: 2-dihydronaphthalene-3-pyridinium-4-oxide (VII). The corstitusion assigned to (VII) is supported by its alternative synthesis from (I) and diethyl malonate or ethyl benzoylacetate in pyridine. Hydrolysis of (VII) gave 1-keto-2-carboxymethylenyl-l: 2-dihydronaphthalene-3-pyridinium-4-oxide which was converted to l-keto-2-carboxyanilidomethylenyl-l : 2-hydronaphthalene-3-pyridinium-4-oxide (IX) and 1-keto-2-methylenyl-l: 2-dihydronaphthalene-3-pyridinium-4-oxide.

The reaction of acetoacetanilide with (I) in pyridine gave (IX) and 1-keto-2-acetomethylenyl-l : 2-dihydronaphthalene-3-pyridinium-4-oxide. The latter was also synthesized from 2-chloro-3-acetonyl-l : 4-naphthoquinone and acetyl acetone by reaction of these substances with (I) in pyridine.

A reaction mechanism to account for the formation of the above compounds is suggested.

We are deeply indebted to the Ministry of Education, Government of India, for the award of a Senior Research Scholarship to one of us (B. S.) and to Dr. T. S. Gore for the microanalyses recorded in the paper.