Extensive effort has been expended to utilize π-allyl palladium-complexes as electrophilic allyl donor intermediates in cooperative dual catalysis, but their counter anions such as carboxylates or alkoxides are almost always discarded as waste. We have developed a cooperative Pd(0)/Rh(II) dual catalysis system that utilizes both the electrophilic allyl and nucleophilic counter anion functionalities inherent in the starting allylic substrates. In this cooperative catalysis, redox compatible Pd(0) and Rh(II) catalysts selectively activate allylic substrates and N-sulfonyl-1,2,3-triazoles to generate π-allyl Pd(II)-complexes and 1,3-ambivalent equivalent aimino Rh(II)-carbenoid intermediates, respectively. The counter anion of the π-allyl Pd(II)-complex acts as a nucleophile transferring to the electrophilic carbenic carbon to form Pd/Rh-associated zwitterionic intermediates, in which the cationic palladium species may coordinate with both counter anion and imine nitrogen in the same plane establishing the (Z)-geometry of the products.

A straightforward route toward construction of α-quaternary chiral β-lactam moiety via Rh(II)/Pd(0)catalyzed stereoselective relay catalytic reaction is reported. This asymmetric dual relay catalysis involves Rh(II)-catalyzed enantioselective intramoluecular C−H insertions of αdiazoamides, and sequential Pd(0)-catalyzed diastereoselective intermolecular allylic alkylation. Under mild reaction conditions, a broad range of α-quaternary allylated chiral βlactams have been synthesized in high yields (up to 99%) with excellent stereoselectivities [up to diastereomeric ratio (dr) >99:1, up to 98% enantiomeric excess (ee)].

A novel divergent tandem one-pot method for the synthesis of 3,5,6-trisubstituted 1H-pyrimidin-2,4-dione derivatives is developed. In the presence of 10 mol % of Cu(OAc)2, the α-substituted Blaise reaction intermediates (R(2) ≠ H) reacted with isocyanates chemoselectively to afford pyrimidin-2,4-diones, whereas the α-unsubstituted Blaise reaction intermediate (R(2) = H) showed a propensity to be a C-nucleophile toward electrophiles, permitting the installation of different functionalities at the 5-position through sequential tandem reactions.

A highly efficient method for the one-pot synthesis of stereocontrolled (Z)-3-methyleneisoindolin-1-ones was developed starting from 2-bromoarylnitriles via tandem sequential reaction with a Reformatsky reagent (Blaise reaction), followed by Pd-catalyzed intramolecular aminocarbonylation with carbon monoxide at 1 atm pressure. It has been found that the conformational flexibility of the bisphophine ligand is of great importance to the success of this tandem aminocarbonylation reaction.

Efficient synthesis of optically active Nfused 1,3-oxazolidines containing quaternary and tertiary stereocenters was achieved via Pd-catalyzed asymmetric (3 + 2) cycloadditions of sulfamatederived cyclic imines and vinylethylene carbonates. Using a chiral phosphoramidite ligand, the cycloadditions proceeded effectively providing sulfamidate-fused 1,3-oxazolidines in high yields (up to 96%) with stereoselectivities (up to 25:1 dr; > 99% ee). Additionally, the scale-up reaction and further transformations of the product were also achieved demonstrating the synthetic utility toward the construction of useful heterocycles such as chiral oxazoline bearing a quaternary stereocenter.Scheme 2. Gram-scale synthesis of sulfamidate-fused 1,3-oxazolidine 3 a and its further applications.