Indolizino quinolines

Indolizino-quinoline 250, the ring system present in camphotecine and mappicine, has been prepared using classical Friedlander reaction under microwave irradiation conditions [160]. The reaction was successfully carried out in AcOH as the solvent and gave good results even with unstable o-amino benzaldehydes 248 (Scheme 92). 

This section is concerned with reactions that result in the fusion of one or more additional rings to the indolizine system. Of course, an indoli-zine synthesis can be designed in which the functional groups are oriented for cyclization. An example is the formation of the indolizino-[l,2-c]quinoline 132 (Scheme 17).199... 

Chemical Name (l,4 -Bipiperidine)-l -carboxylic acid, (4S)-3,4,12,14-tetrahydro-4,ll-diethyl-4-hydroxy-3,4-dioxo-lH-pyrano(3, 4 6,7) indolizino[l,2-b]quinolin-9-yl ester, monohydrochloride... 

Curran and Du reported that the cascade reaction of the isonitriles 520 with B-iodo-Af-propargylpyri-done 521 in the presence of a palladium-catalyst gave the 1 l//-indolizino[l,2-6]quinolin-9-ones 522 in high... 

Asymmetric intermolecular Pauson-Khand reactions have been realized using a number of chiral auxiliaries chelating to the metal and/or attached to the alkyne. One example using a camphor-derived ligand is seen in Scheme 253. Moderate asymmetric induction has been observed using chiral amine A-oxides as the promoter. For example, (+)-indolizino[3,4-b]quinoline A-oxide gave up to 53% ee. 

Tetrahydroindolizinediones 397 reacted with 2-aminobenzaldehydes 396 on heating under reflux in acetic acid for 8h to give indolizino[l,2-Z)]quinolines 398 in 31-51% yields. Under MWI, the yields were improved (57-91%) perhaps owing to the shortened reaction times (15 min) that limited any degradation of unstable reactants (Scheme 80) (02SL2077). 

Indolizino[l,2-c]quinolines. 60%-Perchloric acid added to a soln. of methyl 2- (2-benzamidophenyl) indolizine-l-carboxylate in glacial acetic acid, and allowed to stand 24 hrs. at room temp. 6-benzoyloxyindolizino[l,2-c]quinoline hydroperchlorate. Y 83%. G. Niederdellmann and F. Krohnke, A. 688, 196 (1965). 

Curran and coworkers [141] developed a palladium(0)-catalysed domino process for the synthesis of the very potent anticancer natural product (S)-camptothecin (283) [142] and its analogues (Scheme 8.70). Camptothecin (283) contains an ll//-indolizino[l,2- ]quinolin-9-one skeleton, which is also found in mappicine [143] and the promising new analogue DB-67 (287) [144]. A domino-radical reaction has been used for its construction in 40-60% yield [145]. However, the product is also accessible from the isonitrile 284... 

Electron-rich aryl isonitriles and 6-iodo-iV-propargylpyridones undergo a palladium-catalyzed cascade reaction at ambient temperature to afford llFf-indolizino[l,2-6]quinolin-9-ones in good... 

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