Development of new asymmetric two-center catalysts in phase-transfer reactions

A new asymmetric two-center phase-transfer catalyst was designed and a catalyst library containing more than 40 new two-center catalysts was constructed. The catalysts were applied in phase-transfer alkylations and Michael additions to afford the corresponding products in up to 93% ee and 82% ee, respectively.     

Catalytic asymmetric tandem transformations triggered by conjugate additions

The development of efficient methods to access complex molecules with multistereogenic centers has been a substantial challenge in both academic research and industrial applications. One approach to this challenge is catalytic asymmetric tandem transformations, which allow a rapid increase in molecular complexity from readily available starting materials to produce enantiopure compounds. In recent years, considerable efforts have been directed towards the development of asymmetric tandem transformations. This Minireview highlights recent developments and the applications of metal-catalyzed and organocatalytic asymmetric tandem transformations triggered by conjugate additions.     

催化不对称Michalel加成反应的新进展

总结了近年催化不对称Michael加成反应的新方法，包括手性金属络合物催化 的反应，呈手性Lewis酸性的手性金属络合物促进的不对称加成，手性冠醚络合物 催化的反应及其它催化反应。     

Asymmetric Phase‐Transfer‐Catalyzed Intramolecular N‐Alkylation of Indoles and Pyrroles: A Combined Experimental and Theoretical Investigation

Asymmetric phase‐transfer catalysis (PTC) has risen to prominence over the last decade as a straightforward synthetic methodology for the preparation of pharmacologically active compounds in enantiomerically pure form. However, the complex interplay of weak nonbonded interactions (between catalyst and substrate) that could account for the stereoselection in these processes is still unclear, with tentative pictorial mechanistic representations usually proposed. Here we present a full account dealing with the enantioselective phase‐transfer‐catalyzed intramolecular aza‐Michael reaction (IMAMR) of indolyl esters, as a valuable synthetic tool to obtain added‐value compounds, such as dihydro‐pyrazinoindolinones. A combined computational and experimental investigation has been carried out to elucidate the key mechanistic aspects of this process.     

Catalytic asymmetric phase-transfer reactions using tartrate-derived asymmetric two-center organocatalysts

A new highly versatile asymmetric two-center catalyst, tartrate-derived diammonium salt (TaDiAS), was designed and a catalyst library containing more than 70 new two-center catalysts was constructed. A variety of (S,S)- and (R,R)-TaDiAS were easily synthesized from diethyl l- and d-tartrate, respectively, using common and inexpensive reagents under operationally simple reaction conditions. TaDiAS was used in phase-transfer alkylations and Michael additions to afford various optically active α-amino acid equivalents in up to 93% yield. Moreover, dramatic counter anion effects were observed in phase-transfer catalysis (PTC) for the first time, making it possible to further improve reactivity and selectivity. These findings validate the usefulness of three-dimensional fine-tuning of the catalyst (acetal, Ar, and counter anion) for optimization. Recovery and reuse of the catalyst was also possible using simple procedures. The present asymmetric PTC was successfully applied to enantioselective syntheses of serine protease inhibitor aeruginosin 298-A and its analogues.     

Chiral bidentate bis(n-heterocyclic carbene)-based palladium complexes bearing carboxylate ligands: highly effective catalysts for the enantioselective conjugate addition of arylboronic acids to cyclic enones

Axially chiral cis-chelated bidentate bis(N-heterocyclic carbene)-palladium(II) complexes with two weakly coordinating carboxylate ligands are effective catalysts for the asymmetric conjugate addition of arylboronic acids to cyclic enones, producing the corresponding adducts in moderate-to-high yields and with good-to-high enantioselectivities, in most cases under mild conditions.