Studies on The Reactions of Cyclic Oxalyl Compounds with Oxindole and Lawesson Reagent

摘要

4-Acyl substituted heterocyclic 2,3-diones (1,5), furan- or pyrrole-diones, are versatile starting materials for variety of reactions, generation of α-oxoketenes by thermolysis, cyloaddition of heterocumulenes across the oxa-1,3-diene subunit as well as addition of nucleophiles leading to a number of mono- and bi-cyclic heterocyclic systems. In order to examine if that kind of chemistry can be extended to somewhat modified systems several attempts to change functional groups in 1 and 5, have now been made e.g. transformation of carbonyl groups into the corresponding C=S- moieties using the Lawesson-reagent. Analytical and spectroscopic investigation clearly indicated that instead of the expected sulfurization, the reaction of the furandione with Lawesson reagent (LR) gave highly coloured products 2, which can be regarded as a nonbenzoid oxa analog of Isoindigo. Extending the reaction of furandione 1 with LR to the pyroldione 5, prepared from the reactions of corresponding N,N-dialkylurea and 1a, similar results were obtained.