Organocatalysis:from Homogeneous Bifunctional Activation To Heterogeneous Catalytic Systcm

Complementing biocatalysis and metal-ligand catalysis, organocatalysis has been emerged as a new method for the effective construction of chiral compounds in the field of asymmetric catalysis. Since organocatalysts are easily available, robust, metal-free, non-toxic, and unsensitive to moisture and air, the asymmetric organocatalysis has gained rapid growth in the past decade and become to one of the hottest topics in modern organic chemistry.We are inspired by the pursuit of new reactions in synthetic organic chemistry and of the total synthesis of natural products using organocatalysis. Utilizing the strategy of organic bifunctional catalysis, we made the following progress:1. Based on the concept of vinylogy, we have developed a highly enantio-selective Michael reaction of a,(3-unsaturated y-butyrolactam with enones by using a cinchona alkaloid-based thiourea catalyst. This method, with a broad range of substrates, provides a simple and efficient, and atom-economic access to chiral y-substituted butyrolactams. Consequently, we systematically investigated the reaction mechanism with the combination of NMR experiments and DFT calculations. A new activation model in organic bifunctional catalysis was, therefore, proposed.2. Through asymmetric Henry reaction of isatins catalyzed by 6'-OH- cinchona alkaloid catalyst, we have developed a highly enantioselective method for the synthesis of important 3-hydroxy-2-oxindole scaffold. This method was successfully applied to the total synthesis of (R)-(+)-dioxibrassinin.We noticed that the high catalyst loading is the major shortcoming of organocatalysis in many asymmetric reactions. In order to solve this problem, we attempted to develop functional organic porous materials as effective heterogeneous organocatalysts. Through the "bottom-up" strategy, we realized at first the incorporation of 4-N,N-dimethylamino-pyridine (DMAP) into the network of nanoprous conjugated polymer (NCP). As a new heterogeneous catalyst, DMAP-NCP displays excellent catalytic activity in catalyzing the acylation reaction of alcohols and phenols. Thereafter, we synthesized a new organic porous material embedded with the chiral 2-tritylpyrrolidine organocatalyst. We have obtained the preliminary results on its application in the asymmetric heterogeneous reactions.