ChemInform Abstract: TBAI/TBHP-Catalyzed [3 + 2]Cycloaddition/oxidation/Aromatization Cascade and Online ESI-MS Mechanistic Studies: Synthesis of Pyrrolo[2,1-a]isoquinolines and Indolizino[8,7-b]indoles (original) (raw)
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Chemistry (Weinheim an der Bergstrasse, Germany), 2012
The indium trichloride-catalyzed reaction between aromatic imines and α,β-unsaturated N,N-dimethylhydrazones in acetonitrile afforded 1,2,3,4-tetrahydroquinolines bearing a hydrazone function at C4 through a one-pot diastereoselective domino process that involves the formation of two CC bonds and the controlled generation of two stereocenters, one of which is quaternary. This reaction constitutes the first example of an α,β-unsaturated dimethylhydrazone that behaves as a dienophile in a hetero Diels–Alder reaction. The related reaction between anilines, aromatic aldehydes, and methacrolein dimethylhydrazone in CHCl3 with BF3⋅Et2O as catalyst afforded polysubstituted 1,2,3,3a,4,8b-hexahydropyrrolo[3,2-b]indoles as major products through a fully diastereoselective ABB′C four-component domino process that generates two cycles, three stereocenters, two CC bonds, and two CN bonds in a single operation.
Tetrahedron, 1990
We now report a fundamentally new simple and apparently general method to the synthesis of fused pyrroles, namely, pyrrolo [ 1,2-alquinoxalines, indolo[3,2c]quinolines and indolo [ 1,2-c]quinazolines. Our approach is centered on the aza-Wittig type reaction of iminophosphoranes with heterocumulenes: e.g. isocyanates, isothiocyanates, carbon dioxide and carbon disulfide to give o-pyrrolylphenyl heterocumulenes 1, which subsequently undergo ring closure leading to the fused pyrroles 2 (Chart 1).
Tetrahedron, 2007
The indolo[2,1-a]isoquinoline and pyrrolo[2,1-a]isoquinoline nuclei have been synthesized from N-benzylindole or ethyl 1Hindol-1-ylacetate and N-benzylpyrrole precursors, respectively. Firstly, at C-2 of either the indole or pyrrole nucleus, aromatic rings containing a carbonyl substituent ortho to the newly formed biaryl axis were introduced using the Suzuki-Miyaura coupling reaction. Thereafter, under basic conditions the nucleophile that formed at the acidic methylene protons of the N-benzylindole, ethyl 1H-indol-1-ylacetate or N-benzylpyrrole intermediate reacted with the internal aromatic carbonyl to yield (after the expulsion of water) the title compounds. For example, exposure of ethyl 2-(2-(2-formylphenyl)-1H-indol-1-yl)acetate to potassium tert-butoxide resulted in the formation of ethyl indolo[2,1-a]isoquinoline-6-carboxylate.