Pyrrolo quinoxalines table

According to the data in Table 3.1, of the 12 possible methods for the synthesis of pyrrolo[l,2-a]quinoxalines the most successful are the methods based on the QAl, QBl, QCl, QC2, and QE2 approaches. Methods based on QA2, QA3, QA4, and QB2 can only be realized after effective methods have been developed for the synthesis of Al-alkylated derivatives of quinoxalines with alkyl fragments of various lengths and with various functional groups at the terminal atoms of the alkyl fragment that promote closure of the pyrrole ring, or with participation of the C(2) atom of the quinoxahne system, or with participation of the substituent at position 2 of the quinoxahne system. 

Table 3.2 Synthesis of coumarin bearing pyrrolo[l,2-a]quinoxaline derivatives 208a-j...

Table 3.5 Hydroamination-triggered cyclization strategy for the synthesis of fused pyrrolo[l,2-a] quinoxalines...

As shown in Table 3.8, the cascade reactions were performed well enough for most of 2-iodoanilines with electronrich, electron-neutral, and electron-poor groups to afford corresponding pyrrolo[l,2-ti]quinoxalines in good to excellent yields (entries 1-7). Moreover, heterocyclic aminoiodoarene could also react well enough with a 78 % yield (entry 8). Additionally, aminobromoarene provided a 68 % yield, while aminochloroarene afforded only a trace of the product under the experimental conditions (entries 9 and 10). 

Returning to the synthesis of 2,3-few(benzimidazol-2-yl)quinoxalines 100a-g (Scheme 6.41 Table 6.5) it should be noted that in one case, i.e., in the case of the synthesis of 2,3-fcw(benzimidazol-2-yl)-6-nitroquinoxaline lOOe, the less-reactive l,2-diamino-4-nitrobenzene 5h was used as a reagent. In this case a derivative of pyrrolo[l,2-a]quinoxaline containing one benzimidazolone (in position 1) and two benzimidazole (at positions 2 and 3) fragments in the newly formed pyrrole ring from the reaction mixture were isolated in trace amounts as an unexpected product. The formation of compound 159 could be due to the condensation of 3-(benzimidazo-2-yl) quinoxalin-2(lf/)-one 37s with its predecessor-3-(benzimidazol-2-yl)methylene-... 

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