porous palladium(II)‐polyimines are excellent catalysts for cooperatively catalyzed and enantioselective cascadereactions. In synergy with a chiral amine co‐catalyst, polysubstituted cyclopentenes and spirocyclic oxindoles, including the all‐carbon quaternary stereocenter, were synthesized in high yields. High diastereo‐ and enantioselectivities were achieved for these dynamic kinetic asymmetric transformations
“Organo-Metal” Synergistic Catalysis: The 1+1>2 Effect for the Construction of Spirocyclopentene Oxindoles
作者:Wangsheng Sun、Gongming Zhu、Chongyang Wu、Liang Hong、Rui Wang
DOI:10.1002/chem.201201976
日期:2012.10.29
efficient “organo–metal” synergisticcatalysis strategy for the synthesis of spirocyclopentene oxindole derivatives has been developed (see scheme). The lower overall d.r. and ee obtained from the stepwise approach (4:1 vs. 8:1 d.r.; 71 vs. >99 % ee) suggest that both catalysts function more efficiently when combined, compared with the separate catalytic approach, and show an evident 1+1>2 synergistic effect
The reaction mechanism for the palladium and amine cocatalyzed carbocyclization of aldehydes with alkynes has been investigated by means of density functional theory calculations and experiments. The Pd/amine cocatalyzed transformation is a carbocyclization of in situgenerated enaminynes where the C–C bond-forming step is most likely promoted by a Pd(II) species. Notably, the latent Pd(0)/Pd(II) catalytic