The Study On Rhodium(Ⅱ)/Palladium(0) Dual Catalysis For Synthesis Of 2-Oxindole Derivatives Containing Quaternary Carbons

Dual catalysis is an ideal synthetic strategy which is containing two kinds of catalysts,it is employed to realize the reactivity and selectivity which cannot be achieved by single catalysis through cooperative or relay processes.The research on dual catalysis has been concentrated on developing the system of combining transition metal and organic catalysts,which integrates the virtues of efficiency and high selectivity both.Compared with the system of metal-organic,dual transition metal catalyzed reactions are being developed more slowly though discovered earlier,primary because of the compatibility between two transition metal catalysts and the mechanism of dual transition metal catalysis.Therefore,it is a challenging task that developing dual transition metal catalysis systems.In this thesis,we mainly employed the rhodium（Ⅱ）/palladium（0）dual catalyzed tandem rhodium（Ⅱ）catalyzed intramolecular C-H insertion and palladium（0）catalyzed allylic alkylation of 2-diazo-3-oxo-butanamides and allylic esters,and as a result,we obtained the series of 2-oxindoles containing quaternary centers at 3-position.On the primary mechanistic study,we proposed the reaction is been through the relay process.Based on the research,we have achieved the following results:1.Extended the substrate compatibility of rhodium（Ⅱ）/palladium（0）dual catalytic system,and developed a new method to synthesize substituted 2-oxindoles containing quaternary centers.Through optimization of reaction condition,we obtained substituted 3-allylic-3-acyl-2-oxindoles in 50%-97%yields by using 1 mol%Rh（^tBu CO₂）₄,2 mol%[Pd（allyl）Cl]₂,4.8mol%Xantphos as dual catalytic system in toluene under N₂ at 50°C.The reaction was still efficient when the scale was enlarged.2.Determined the reaction process as Rh（Ⅱ）/Pd（0）relay catalysis.In the stepwise reaction,3-acyl-2-oxindole can be obtained by rhodium（Ⅱ）catalyzed decomposition of diazo substrates,which was carried out allylic alkylation in another independent palladium（0）catalytic circle to afford the target products.On the other hand,there was no enantioselective product by employing chiral rhodium catalysts.