4- Arylamino-8-iodoquinoline

Treatment of 4-arylamino-8-iodoquinoline 268 with propargyl alcohol in presence of iodo(phenyl)bis(triphenylphosphine) palladium and copper (I)iodide afforded 269 which upon catalytic reduction using Linder s catalyst gave 4//-pyrrolo[3,2,l-(/]quinoline 270 (97H2395) (Scheme 48). 

Other indoles that have been prepared using the Sonogashira coupling and cyclization sequence include 5,7-difluoroindole and 5,6,7-trifluoroindole [219], 4-, 5-, and 7-methoxyindoles and 5-, 6-, and 7-(triisopropylsilyl)oxyindoles [220], the 5,6-dichloroindole SB 242784, a compound in development for the treatment of osteoporosis [221], 5-azaindoles [222], 7-azaindoles [160], 2,2-biindolyls [223,176], 2-octylindole for use in a synthesis of carazostatin [224], chiral indole precursors for syntheses of carbazoquinocins A and D [225], a series of 5,7-disubstituted indoles [226], a pyrrolo[2,3-eJindole [226], an indolo[7,6-g]indole [227], pyrrolo[3,2,l-y]quinolines from 4-arylamino-8-iodoquinolines [228], optically active indol-2-ylarylcarbinols [229], 2-alkynylindoles [176], 7-substituted indoles via the lithiation of the intermediate 2-alkynylaniline derivative [230], and a variety of 2,5,6-trisubstituted indoles [231], This latter study employs tetrabutylammonium fluoride, instead of Cul or alkoxide, to effect the final cyclization of 215 to indoles 216 as summarized here. 

As part of their study on gastric (H+/K+)-ATPase inhibitors, Kang et al. developed a simple and convenient synthetic approach to 1,2,3-trisubstituted pyrrolo[3,2-c]quinolines by means of Pd-catalyzed heteroannulation of 4-amino-3-iodoquinoline derivatives with internal alkynes [76]. The following scheme shows an example of a reaction using 4-arylamino-3-iodoquinoline derivative 180 with alkyne 181 to provide 1-arylpyrrolo [3,2-c]quinoline 182, illustrating the possibility of introducing diverse substituents to 1-arylpyrrolo[3,2-c]quinolines. In addition, a Pd-catalyzed domino hydroarylation/ cyclization process was reported to form substituted quinolines [77]. Thus, 3-arylquino-lines were prepared in 56-74% yield when 3,3-diethyl-l-phenyl-1-propyne and aryl iodide were refluxed in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate [(bmim)BF4 ],in the presence of HCO2H, EtjN, and palladium catalyst. Meanwhile,... 

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