Preparation Of Mesoporous Silicone Nanomaterials And Its Application In Series Reaction

Multiple-step organic transformations in one-pot catalytic process, as an important aspect of green chemistry, have attracted a great deal of interest due to atomic economy and minimum workup. However, intrinsic disadvantages, such as reuse of expensive organometallic complexes and product contamination from leaching, do still hinder practical applications in industrial process. Thus, development of an immobilized strategy overcomes these barriers is of considerable importance. Silica-based mesoporous materials as supports to immobilize organometallic complexes have exhibited some attracting features in catalysis. Furthermore, an important challenge in asymmetric cascade reactions is solving the intrinsic incompatibility of the two distinct types of organometallic complexes that participate in a one-pot catalytic processs. How to adjust the extrinsic conflict imposed on the reaction conditions is another synthetic problem. Although a catalytic cascade reaction should theoretically display a higher efficiency than the corresponding two single-step reaction because it involves several transformations in situ, most cascade reactions are still based on the compatible pairs of organometallic complexes. Therefore, investigations to overcome the incompatible nature of distinct organometallic complexes is warranted towards the development of a general and practical, one-pot enantio-relay catalytic process.(1) Suzuki cross-coupling reaction of aryl halides and arylboronic acids, and catalytic reduction of carbonyls are two classic organic reactions, which have been investigated extensively both in theoretically and practically. The design of mesoporous silica-supported organopalladium-functionalized heterogeneous catalysts for one-pot tandem Suzuki cross coupling-reduction of haloacetophenones and arylboronic acids to prepare a range of biaryl alcohols is still a scientific challenge. Firstly, We take advantage of an imidazolium-based organic-inorganic hybrid silica(IBOIHS) as a support and develop an organopalladium-functionalized heterogeneous catalyst(Pd PPh2-IBOIHS), can catalysis one-pot tandem Suzuki cross coupling–reduction of haloacetophenones and arylboronic acids, providing a range of biaryl alcohols with high yields. Secondly, Our synthetic strategy involves a dual-immobilization approach, in which a site-isolated imidazolium-based organopalladium-functionality is immobilized within an organic–inorganic hybrid silica, whilst a N-sulfonylateddiamine-based organoruthenium-functionality is easily anchored within ethylene-coated magnetic nanoparticles. The dual-immobilization approach efficiently eliminates the interactions of the two distinct organometallic complexes and overcomes their incompatibility. At last, the strategy done in the present study is based on a co-condensation method, where the site-isolated organopalladium-functionality and N-sulfonylated diamine-based organoruthenium-functionality are immobilized within a single periodic mesoporous organosilica. Such a strategy eliminates the interactions between the organometallic complexes and thereby overcomes their incompatibility. As expected, the Ru/Pd-bifunctionalized PMO efficiently catalyzed one-pot cascade asymmetric transfer hydrogenation and Suzuki cross-coupling of haloacetophenones and arylboronic acids to various chiral biaryl alcohols in aqueous medium.(2) Chiral β-hydroxy sulfones are a kind of important optically active alcohols, which are essential building blocks for several bioactive molecules. Because of electron withdrawing property of sulfonyl group at the β-position, the α-carbon could be further functionalized and sulfonyl group could be removed without racemization. For now, asymmetric reduction of β-keto sulfones is a common way to get chiral β-hydroxy sulfones. Though high yields and enantioselectivities were attained, the high pressure of reactions made them difficult to be operated. However, pure β-keto sulfones have to be obtained most of reported processes, which needs long production cycle and high cost of products. So, we design a novel catalytic procedure for one-pot, two-step synthesis of optically active β-hydroxy sulfones from α-bromoketones and sodium sulfinates in aqueous medium.