Quinoxaline, pyrrole-fused

In 1980, Ames et al. reported a related pyrrole formation catalyzed by mer-cury(II) [98], Pyrrole-fused quinoxaline 204 was obtained by treatment of a 2-amino-3-alkynylquinoxaline derivative 203 with a catalytic amount of Hg(OAc)2 (Scheme 19.53). On the other hand, dichloroquinoxaline 205, the precursor of 203, was converted directly to 204 under reaction conditions for Sonogashira coupling with phenylacetylene. A related palladium(II)-catalyzed pyrrole synthesis using 1-aminoalk-3-yn-2-ols 206 was reported by Utimoto, Nozaki and co-workers in 1981 (Scheme 19.54) [99]. It should be noted that PdCl2 showed excellent turnover to produce the corresponding pyrroles 207 in good yields with only 0.1 to 1 mol % catalyst loading. 

Scheme 3) <05TL2189>. However, in this case the reaction did not afford the expected DA adduct, the product being the porphyrin derivative 10 resulting from the tetradehydrogenation of the corresponding adduct. The porphyrin derivative 11 was also obtained although in minor amount this product must result from a cyclization reaction between the beta-fused quinoxaline ring and the adjacent maso-aryl group. Also, bisadducts 12 and 13 were isolated these are the result of site specific bisaddition to opposite pyrrolic rings followed by oxidative processes.

Thus, a rare one-pot reaction for assembling pyrrolo[l,2-fl]quinoxalines from 1-(2-nitrophenyl)pyrroles and various alcohols. The nitro reduction, alcohol oxidation, heterocycle formation, and heterocycle oxidation were realized in a cascade. A wide range of these fused heterocycles bearing different alkyl and aryl groups in position 4 have been elaborated from suitable substrates thereby 3-nitro-2-pyrrolopyridine was also compatible with this process, giving the corresponding fused tricyclic compounds. 

Cheeseman GWH, Tuck B (1965b) Further syntheses and properties of p5urolo[l,2-a]quinoxa-lines. J Chem Soc 3678-3687. doi 10.1039/JR9650003678 Cheeseman GWH, Tuck B (1966) The synthesis of p5UTolo[l,2-a]quinoxahnes from N-(2-acylaminophenyl)pyrroles. J Chem Soc C 852-855 Chicharro R, Castro S, Reino JL, Aran VJ (2003) Synthesis of tri- and tetracyclic condensed quinoxalin-2-ones fused across the C-3-N-4 bond. Eur J Org Chem 12 2314—2326. doi 10. 1002/ejoc.200300028... 

The Diels-Alder reaction of weio-tetraarylporphyrins with the pyrazine o-quino-dimethane mainly affords the oxidized compounds 55a-c instead of the expected chlorin adducts (Scheme 5.14). The bis-addition is site specific, occurring in opposite pyrrolic rings and leads to compounds 57 and 58. The novel polycyclic products 56a-c, 58a, and 58b result from the coupling reactions between the p-fused quinoxaline ring and one adjacent meso-atyl group. It should be pointed out that, in contrast to compounds 55a and 57a, there also occurs the combination between one of the orto-atoms of the carbon of the mew-aryl group and one of the carbon atoms of the benzene ring quinoxaline system in the fonnalion of compounds 56a and 58a. 

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