Synthesis of 2-spiropseudoindoxyls via an intramolecular nitroalkyne redox-dipolar cycloaddition cascade
Novel spiropseudoindoxyls were synthesized in high yields via a fully regioselective Au(III)-catalyzed cycloisomerization of easily obtainable o-nitrophenylpropiolamides, followed by an intramolecular dipolar cycloaddition as key steps. This one-pot cascade reaction resulted in new tetracyclic pseudoindoxyls, which were hydrogenated toward the title compounds as single diastereomers via N-O cleavage. The mechanism of the gold catalyzed cycloisomerization was studied by DFT and suggests a reaction path without the intermediacy of gold carbenoid species in these cases.
Gold-catalyzed stereoselective synthesis of azacyclic compounds through a redox/[2 + 2 + 1] cycloaddition cascade of nitroalkyne substrates
We report a new redox/cycloaddition cascade on readily available 1-alkynyl-2-nitrobenzenes that produces complex azacyclic compounds stereoselectively. The core structures of the resulting products are constructed through a formal [2 + 2 + 1] cycloaddition among α-carbonyl carbenoids, nitroso species, and external alkenes.
o-Chloro- and o-bromonitrobenzenes are efficiently converted to 6-substituted indoles in a four step synthesis, proceeding through o-trimethylsilylethynylnitrobenzenes, o-nitrophenylacetaldehyde dimethylacetals and o-aminophenylacetaldehyde dimethylacetal
Tischler, Allan N.,Lanza, Thomas J.
p. 1653 - 1656
(2007/10/02)
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