Synthesis of some substituted quinoxalines and polycyclic systems containing the quinoxaline nucleus

Abstract

The synthesis is described of quinoxalines 11,14,15,16,20,21,23 and 25 of interest as intermediates. The preparation of 21 from 3 by the action of thiourea and the formation of the hexaazapentacycle 23 from sulfide 20 and butylamine are discussed. The methylation of the dione 10 is reinvestigated and the product found to be a mixture of 29 and 30. The preparation of dimethoxyquinoxaline podands, e.g. 32, 33,34,40 and 41, tricyclic crown ether 31 and pentacyclic crown ethers, e.g. 38, is described and the effects of metal ions on spectroscopic properties of 40 and 41 are reported.Our objective was the synthesis of some 5,8-and 6,7dimethoxyquinoxalines. These compounds are of interest as fluorophores and the 5,8-dimethoxy series is a potential precursor of the corresponding p-quinones, useful as starting materials for the synthesis of tricyclic quinones through the Diels-Alder reaction. In the course of the work, we have uncovered some reactions leading to linear fused pentacyclic systems which may have interesting electronic or optoelectronic properties.2A well-tried route to quinoxalines is the reaction of the appropriate o-phenylene diamine with a 1,2-dicarbonyl compound. Unfortunately, although the nitration of 1,4dimethoxybenzene gives the required 2,3-dinitro derivative as the major product, it is accompanied by the isomeric 1,4-dimetho~y-2,5-dinitrobenzene,~-' and this unwanted product is difficult to remove when the nitration is performed on a large scale. In the present work, the mixture of dinitro isomers was hydrogenated over a palladium-on-carbon catalyst and the resulting mixture of diamines was quickly treated with the appropriate dicarbonyl compound whereupon only the odiamine gave the quinoxaline. The products formed by the reaction of the p-diamine were easily removed. In this way, the known 5,8-dimethoxy-2,3-disubstituted quinoxalines, 1, 26 and the quinoxalinedione lo6 were readily obtained and the last was converted to the dichloroquinoxaline, 3.6 This dichloro

First example of a copper(i)–water bond. Synthesis and structure of polymeric poly-μ-2,3-diphenylquinoxaline–(aqua)copper(i) cation

“…Reaction of opda with benzil also yields L 3 . 6 The hydrazine formed in situ reduces Cu 2+ to Cu + . One of the products isolated from this reaction mixture is the perchlorate salt of the polymeric cationic copper(i) complex of L 3 and water, {[CuL 3 (H 2 O)]ClO 4 •0.5C 2 H 5 OH} n 1.…”

Diquino[3,4-b;4′,3′-e][1,4]dithiine

“…Thia-and azapentacycles are considered to be a new type of electron donor (Boros et al, 1998;Ahmad et al, 1996;Marti et al, 1994;Engman et al, 1988), which show photoelectric properties (Yoshida et al, 1994) and constitute the active layer in a field-effect transistor (FET) device (Miao et al, 2003). The diazadithiapentaphenes (I) and (II) (common names: isothioquinanthrene and thioquinanthrene, respectively) and the diazadithiapentacenes (III) and (IV) have proved to be excellent substrates in the search for new quinoline derivatives via 1,4-dithiine ring-opening reactions (e.g.…”

Diquino[4,3-b;3′,4′-e][1,4]thiaselenine

“…Pentacyclic heterocycles are considered as a new type of electron donor (Boros & Harfenist, 1998;Ahmad et al, 1996;Marti et al, 1994;Engman et al, 1988). They show photoelectric properties (Yoshida et al, 1994) and constitute the active layer in a field-effect transistor (FET) device (Miao et al, 2003).…”