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941.
《Comptes Rendus Chimie》2014,17(7-8):775-784
Four types of SBA-15 were prepared with different times and temperatures of treatment in order to obtain a range of micropore sizes. CO oxidation was used as a probe reaction in order to evaluate the nature of the active species when SBA-15s were doped with ca 10% Ag deposited from an AgNO3 solution and calcined or reduced at 350 °C. The texture (TEM, nitrogen physisorption), structure (XRD) and reducibility (TPR) of the various catalysts (Ag/SBA-15) were studied and compared to those of a catalyst prepared by deposition of silver on fumed silica as a reference. These catalysts differ initially by the nature of silica and by pore sizes. In CO oxidation, pre-reduced catalysts are more active than pre-oxidised ones. This has to do with two phenomena, i.e. sintering, which produces large inactive silver particles, and formation of active silver species in the form of small Ag2O particles. 相似文献
942.
943.
Highly Selective Dimerization and Trimerization of Isobutene to Linearly Linked Products by Using Nickel Catalysts 下载免费PDF全文
Prof. Arno Behr Nils Rentmeister Thomas Seidensticker Jonas Vosberg Dr. Stephan Peitz Dr. Dietrich Maschmeyer 《化学:亚洲杂志》2014,9(2):596-601
The unique linear linkage of isobutene to generate highly valuable C8 precursors for plasticizers is feasible by using special nickel catalysts. (4‐Cyclooctene‐1‐yl)(1,1,1,5,5,5‐hexafluoro‐2,4‐acetylacetonato)nickel and aluminum‐alkyl‐activated nickel acetylacetonates produce isobutene dimers with high selectivities of up to 95 %. Moreover, selectivity for the head‐to‐head products (2,5‐dimethylhexenes) is remarkably high at up to 99 %. Additionally, novel C12 isobutene trimers are also formed with a very high selectivity of up to 99 % for the linear linkage. The trimer structure (2,5,8‐trimethylnonenes) reflects the stepwise characteristic of the reaction mechanism. Pathways of insertion and activation and the deactivation processes of the catalyst are discussed in detail. 相似文献
944.
The catalytic cross‐dehydrogenative coupling (CDC) reaction has received intense attention in recent years. The attractive feature of this coupling process is the formation of a C? C bond from two C? H moieties under oxidative conditions. In this Focus Review, recent advances in the palladium‐catalyzed CDC reactions of C(sp2)? H bond are summarized, with a focus on the period from 2011 to early 2013. 相似文献
945.
Sulfur‐containing molecules such as thioethers are commonly found in chemical biology, organic synthesis, and materials chemistry. While many reliable methods have been developed for preparing these compounds, harsh reaction conditions are usually required in the traditional methods. The transition metals have been applied in this field, and the palladium‐catalyzed coupling of thiols with aryl halides and pseudo halides is one of the most important methods in the synthesis of thioethers. Other metals have also been used for the same purpose. Here, we summarize recent efforts in metal‐catalyzed C? S bond cross‐coupling reactions, focusing especially on the coupling of thiols with aryl‐ and vinyl halides based on different metals. 相似文献
946.
947.
Copper‐Catalyzed NH Insertion and Oxidative Aromatization Cascade: Facile Synthesis of 2‐Arylaminophenols 下载免费PDF全文
Dong Ding Xiaobing Lv Dr. Jian Li Guangyang Xu Dr. Bing Ma Prof. Dr. Jiangtao Sun 《化学:亚洲杂志》2014,9(6):1539-1542
A copper‐catalyzed cascade reaction of N‐H insertion and oxidative aromatization has been developed. 2‐Arylaminophenols have been prepared in moderate to high yields from the diazo substrates. Moreover, this newly established methodology allows efficient access to natural 1‐oxygenated carbazole alkaloids, such as glycozolicine and murrayafoline A. 相似文献
948.
Site‐Selective CH Borylation of Quinolines at the C8 Position Catalyzed by a Silica‐Supported Phosphane–Iridium System 下载免费PDF全文
Shota Konishi Dr. Soichiro Kawamorita Dr. Tomohiro Iwai Prof. Patrick G. Steel Prof. Dr. Todd B. Marder Prof. Dr. Masaya Sawamura 《化学:亚洲杂志》2014,9(2):434-438
Site‐selective C? H borylation of quinoline derivatives at the C8 position has been achieved by using a heterogeneous Ir catalyst system based on a silica‐supported cage‐type monophosphane ligand SMAP. The efficient synthesis of a corticotropin‐releasing factor1 (CRF1) receptor antagonist based on a late‐stage C? H borylation strategy demonstrates the utility of the C8 borylation reaction. 相似文献
949.
Dr. Seiji Shirakawa Dr. Lijia Wang Dr. Rongjun He Dr. Satoru Arimitsu Prof. Dr. Keiji Maruoka 《化学:亚洲杂志》2014,9(6):1586-1593
Although phase‐transfer reactions catalyzed by using quaternary ammonium salts are generally believed to require base additives, we discovered that, even without any base additives, conjugate additions of 3‐substituted oxindoles to nitroolefins proceeded smoothly in the presence of lipophilic quaternary ammonium bromide under water–organic biphasic conditions. The mechanism of this novel base‐free neutral phase‐transfer reaction system is investigated and the assumed catalytic cycle is presented together with interesting effects of water and lipophilicity of the phase‐transfer catalyst. The base‐free neutral phase‐transfer reaction system can be applied to highly enantioselective conjugate addition and aldol reactions under the influence of chiral bifunctional ammonium bromides as key catalysts. The structure of the chiral ammonium enolate intermediate is discussed based on the single‐crystal X‐ray structures of relevant ammonium salts and the importance of bifunctional design of catalyst is clearly explained in the model of intermediate. 相似文献
950.