Organosilica-Modified Mesoporous Materials Applid In Organic Synthesis And Drugs Deliver

Ordered mesoporous silica materials with stable mesostructure, large surface areas, good biocompatibility, and tailorable size of mesopores in nanometer scale have attracted much attention. We report here the methods to construct organosilica- modified mesoporous materials applied in organic synthesis and drugs deliver. Moreover, we use a simple organosilica compound to synthesize mesoporous silica with nanoscale partical sizes.Palladium catalyst has been wildly used for organic synthesis because it affects an extraordinary number of very different reactions and tolerates a wide variety of functional groups. Many palladium-catalyzed carbon-carbon bond-forming reactions such as coupling reaction, Heck reaction, Sonogashira coupling, Tsuji-Trost allylation, etc., have become very important organic transformations in modern synthetic organic chemistry. However, they usually suffer from the high loading of the palladium catalyst. In most of cases up to 5 mol% of the catalysts have been used, which may have a very serious negative impact on their possible industrial application. Thus, development of supported palladium catalysts showing much higher catalytic activity without leaching is highly desirable. A highly active heterogeneous palladium catalyst was prepared from coated mesoporous materials, which contain a layer of readily available PEG with labile coordinating ability for palladium. Its structure has been characterized with TEM, XRD, nitrogen adsorption-desorption, and XPS analysis. The new catalyst showed a very high catalytic activity for Suzuki coupling reaction in water and was still catalytically active after exposing to air for up to 6 weeks. The aqueous suspension of the catalyst may be reused by simple extraction of the aqueous reaction mixture with ether to remove the product. With the addition of S-phos, even C-Cl bond can be activated in Suzuki-coupling reaction. Moreover, this palladium catalyst may be used in other important organic reactions, such as Heck reaction and hydrogenation.Secondly, an efficient pH-responsive carrier system has been constructed by oppositely charged ionic interaction between carboxylic acid-modified SBA-15 silica rods and polyelectrolyte. Active molecules such as vancomycin can be stored and released from the pore voids of SBA-15 by changing pH values at will. The amount of vancomycin stored in the pores of sample based on carboxylic acid modified SBA-15 rods and PDDA is up to 36.4 wt % at pH 6.8. When pH at mild acidity, vancomycin is steadily released from the pores of SBA-15. Both nitrogen adsorption-desorption isothems and XRD patterns show that this system possesses of stable mesostructure, which will be considered an interesting alternative to polymeric delivery system.Furthermore, we use a simple and efficient route to synthesize mesoporous silica with nanoscale partical sizes. Mesoporous silica with particle sizes of around 50 nm and uniform pore sizes of 6.2 nm has been successfully synthesized using a novel organosilane for suppressing the size growth of particles. The synthesis of mesoporous silica with nanoscale particle sizes should be attributed directly to the use of a novel organosilane rather than the other reasons, because during the systhesis all conditions are completely same as those of SBA-15, expect for adding organosilane. Other organosilanes such as 3-mercaptopropyltriethoxysilane and 3-aminopropyltriethoxysilane are also used in the synthesis of mesoporous silica materials, but obtained samples exhibits the sizes with microscales. Obviously, organosilane has a long group, which is effective for suppression of size growth of particles. Generally, due to hydrophilicity of ethoxy groups, organosilane could be homogeneously dispersed around the nanoparticles of silica-micelle composites, forming an organic layer. Possibly, this organic layer with long and hydrophilic groups restrains the aggregation of these nanoparticles, leading to the formation of mesoporous silica materials with nanoscale particle sizes.On the other hand, transition-metal-catalyzed reactions for the synthesis of heterocyclic compounds have been considered as one of the most powerful protocols in modern synthetic organic chemistry. Pyrazolidines are an interesting class of heterocyclic compounds with biological activities attracting scientists to design novel therapeutic agents with mimetic scaffolds. One of the major challenges in these objectives is the development of efficient methods for the enantioselective synthesis of optically active pyrazolidines. However, asymmetric transition-metal-catalyzed reactions for optically active pyrazolidines have not been well developed. We show here an efficient method for enantioselective synthesis of pyrazolidine derivatives. This method was developed via asymmetric palladium-catalyzed cyclization of hydrazine allene with organic halides. Highly diastereo- (up to 95/5) and enantioselective (up to 99%) pyrazolidines were obtained from the easy available and diversely substituted starting compounds.Moreover, to further identify the possibility of asymmetric catalytic system, achiral hydrazine allene was used for coupling-cyclization reaction in the system of Pd(OAc)2 / ligand under the optimized condition. Interestingly, desired optically active pyrazolidines in moderate yield with good enantioselectivity were obtained. These reactions paved the way for asymmetric cyclization of functionalized allene for enantionselective synthesis of other optical active heterocyclic compounds.In summary, organosilica-modified mesoporous materials applied in organic synthesis and drugs deliver were developed and we use a simple and efficient route to synthesize mesoporous silica with nanoscale partical sizes. On the other hand, we report here an efficient method for highly enantioselective synthesis of pyrazolidine derivatives.