Synthesis of pyrroloquinolones

Synthesis of pyrrolo[2,3-g]-and pyrrolo[3,2-f]quinolines from 5-amino-2,3-dimethyl-and 1,2,3-trimethylindoles with 4,4,4-trifluoroacetoacetic ester

“…In contrast to acetoacetate ester [5] we have found that its analog fully fluorinated at the acetyl group reacts with 5-amino-2,3-dimethyl-and -1,2,3-trimethylindoles 1, 2 under the same conditions (refluxing in absolute benzene with traces of glacial acetic acid) to give reaction products involving not only the carbonyl but also the carbethoxy group (principally).…”

“…Thus the acid cyclization of the amides 5, 6 takes place at position 6 of the indole to give exclusively the pyrrolo [2,3-g]quinolones and this differs from the nonfluorinated analogs (prepared from diketene and aminoindoles) which give a mixture of linear and angular products [7] under similar conditions. By contrast to these the pyrrolo[3,2-f]quinolones with a methyl and trifluoromethyl substituent in a peri-position are problematic, probably because of the large steric demand of the trifluoromethyl group when compared with the methyl.…”

“…The UV spectra of the fluorinated enaminocrotonates show two absorption bands which agree with the pattern of the spectra of the nonfluorinated analogs reported in the literature [5].…”

“…[7], compound 11 is a hypothetical structure. The formation of monomethylation products is excluded by the reaction conditions which use an excess of dimethyl sulfate and, evidently, involve identical acidities for the quinolone and pyrrole N-H groups.…”

cis-trans isomerism of indolyl-enaminocarbonyl compounds

“…The synthesis of the studied enamines has been described previously [6][7][8][9][10][11][12][13][14][15][16].…”