Synthesis of Indolo[1,2-a]quinoxalinones through Palladium/Copper-Cocatalyzed Oxidative Isocyanide-Insertion Cyclization of Indoles and Hydrolysis of Enamines
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AbstractA novel Pd/Cu-cocatalyzed isocyanide-insertion cyclization of indoles and hydrolysis of enamines has been developed for the construction of indolo[1,2-a]quinoxalinones. A secondary amine group on the N-phenylindole skeleton acts as an important directing groups that participates in activation of the C(2)-position of the indole and the subsequent isocyanide-insertion cyclization. The fragile generated enamine bond is easily hydrolyzed by the acid medium to give the corresponding quinoxalinone skeleton. This regioselective and high-yielding transformation, which avoids the use of hazardous CO gas, might be extendable to syntheses of natural polycyclic products.
1989 ◽
Vol 30
(22)
◽
pp. 2897-2900
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