928-89-2Relevant articles and documents
Synthesis of 11-methyl-13-azabicyclo[7.3.1]trideca-3,10-diene, a macrobicycle with the 9b-azaphenalene carbon framework, based on the combination of allylboration and intramolecular metathesis
Kuznetsov, N. Yu.,Khrustalev,Strelkova,Bubnov, Yu. N.
, p. 2502 - 2508 (2014)
A four-step synthesis of 11-methyl-13-azabicyclo[7.3.1]trideca-3,10-diene, a potential precursor of the ladybugs defensive alkaloids precoccinelline and mirrhine, has been accom-plished. Treatment of 4-picoline with 5-hexenyl-1-lithium, triallylborane, and methanol led to the synthesis of trans-6-allyl-2-(hex-5-enyl)-4-methyl-1,2,3,6-tetrahydropyridine, which reacted with triallylborane upon heating to be converted to the cis-isomer. A subsequent cyclization of the cis-isomer of N-Boc derivative via the intramolecular metathesis using Grubbs II and Hoveyda - Grubbs II ruthenium catalysts furnished the target bridged macrobicycle. The structure of its hydrochloride was confirmed by single crystal X-ray diffraction studies. The optimal conditions for the metathesis reaction and the isolation of the macrobicyclic product were selected.
Controlling the performance of a silver co-catalyst by a palladium core in TiO2-photocatalyzed alkyne semihydrogenation and H2 production
Fudo, Eri,Imai, Shota,Kojima, Yasumi,Kominami, Hiroshi,Tanaka, Atsuhiro
, (2021/08/24)
Titanium (IV) oxide (TiO2) having palladium (Pd) core-silver (Ag) shell nanoparticles (Pd@Ag/TiO2) was prepared by using a two-step (Pd first and then Ag) photodeposition method. The core-shell structure of the nanoparticles having various Ag contents (shell thicknesses) and the electron states of Pd and Ag were investigated by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The effect of the Pd core and the Ag shell was evaluated by hydrogenation of 4-octyne in alcohol suspensions of a photocatalyst under argon and light irradiation. 4-Octyne was fully hydrogenated to 4-octane over Pd/TiO2, whereas 4-octyne was selectively hydrogenated to cis-4-octene over Pd(0.2)@Ag(0.5)/TiO2. Further increase in the Ag content resulted in a decrease in the conversion of 4-octyne. Pd-free Ag/TiO2 was inactive for hydrogenation of alkyne and induced coupling of active hydrogen species (H2 production). Photocatalytic reactions at various temperatures revealed that the change in selectivity (semihydrogenation or H2 production) can be explained by the difference in values of activation energy of the two reactions. An applicability test showed that the Pd@Ag/TiO2 photocatalyst can be used for hydrogenation of various alkynes to alkenes.
Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes
Geng, Jiao,Hu, Xingbang,Liu, Qiang,Wu, Youting,Yang, Liu,Yao, Chenfei
, p. 3685 - 3690 (2021/05/31)
Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.
Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H2 Gas
Imai, Shota,Nakanishi, Kousuke,Tanaka, Atsuhiro,Kominami, Hiroshi
, p. 1609 - 1616 (2020/02/15)
Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core-Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two-step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. Thus-prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4-octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4-Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4-octyne was semihydrogenated to cis-4-octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4-octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed.
Unexpectedly selective hydrogenation of phenylacetylene to styrene on titania supported platinum photocatalyst under 385 nm monochromatic light irradiation
Lian, Juhong,Chai, Yuchao,Qi, Yu,Guo, Xiangyang,Guan, Naijia,Li, Landong,Zhang, Fuxiang
, p. 598 - 603 (2020/01/28)
Conversion of alkynes to alkenes by photocatalysis has inspired extensive interest, but it is still challenging to obtain both high conversion and selectivity. Here we first demonstrate the photocatalytic conversion of phenylacetylene (PLE) to styrene (STE) with both high conversion and selectivity by using the titania (TiO2) supported platinum (Pt) as photocatalyst under 385 nm monochromatic light irradiation. It is demonstrated that the conversion rate of PLE is strongly dependent on the content of Pt cocatalyst loaded on the surface of TiO2. Based on our optimization, the conversion of PLE and the selectivity towards STE on the 1 wt% Pt/TiO2 photocatalyst can unexpectedly reach as high as 92.4% and 91.3%, respectively. The highly selective photocatalytic hydrogenation can well be extended to the conversion of other typical alkynes to alkenes, demonstrating the generality of selective hydrogenation of C≡C over the Pt/TiO2 photocatalyst.
Visible light-induced diastereoselective semihydrogenation of alkynes to cis-alkenes over an organically modified titanium(IV) oxide photocatalyst having a metal co-catalyst
Fukui, Makoto,Omori, Yuya,Kitagawa, Shin-ya,Tanaka, Atsuhiro,Hashimoto, Keiji,Kominami, Hiroshi
, p. 36 - 42 (2019/05/04)
Hydrogen (H2)-free and poison (lead and quinoline)-free semihydrogenation of alkynes to cis-alkenes under gentle conditions is one of the challenges to be solved. In this study, a titanium(IV) oxide photocatalyst having two functions (visible light responsiveness and semihydrogenation activity) was prepared by modification with 2,3-dihydroxynaphthalene (DHN) and a copper (Cu) co-catalyst, respectively. The photocatalyst (DHN/TiO2-Cu) showed high performance for diastereoselective semihydrogenation of alkynes to cis-alkenes in water-acetonitrile solution under visible light irradiation without the use of H2 and poisons. Alkynes having reducible functional groups were converted to the corresponding alkenes with the functional groups being preserved. The addition of water to acetonitrile changed the amount of alkynes adsorbed on the photocatalyst, which was a decisive factor determining the rate of hydrogenation. A relatively large apparent activation energy, 27 kJ mol?1, was obtained by a kinetic study, indicating that the rate-determining step of this reaction was not an electron production process but a thermal catalytic semihydrogenation process over the Cu co-catalyst. Semihydrogenation and hydrogen evolution occurred competitively on Cu metals and the former became predominant at slightly elevated temperatures, which is discussed on the basis of the kinetic parameters of two reactions.
Supported palladium membrane reactor architecture for electrocatalytic hydrogenation
Delima, Roxanna S.,Sherbo, Rebecca S.,Dvorak, David J.,Kurimoto, Aiko,Berlinguette, Curtis P.
, p. 26586 - 26595 (2019/12/04)
Electrolytic palladium membrane reactors offer a means to perform hydrogenation chemistry utilizing electrolytically produced hydrogen derived from water instead of hydrogen gas. While previous embodiments of these reactors employed thick (≥25 μm) palladium foil membranes, we report here that the amount of palladium can be reduced by depositing a thin (1-2 μm) layer of palladium onto a porous polytetrafluoroethylene (PTFE) support. The supported palladium membrane can be designed to ensure the fast diffusion of reagent and hydrogen to the palladium layer. The hydrogenation of 1-hexyne, for example, shows that the supported Pd/PTFE membrane can achieve reaction rates (e.g., 0.71 mmol h-1) which are comparable to 0.92 mmol h-1 measured for palladium membranes with a high-surface area palladium electrocatalyst layer. The root cause of these comparable rates is that the high porosity of PTFE enables a 12-fold increase in electrocatalytic surface area compared to planar palladium foil membranes. These results provide a pathway for designing a cost-effective and potentially scalable electrolytic palladium membrane reactor.
Palladium-Catalyzed Electrochemical Allylic Alkylation between Alkyl and Allylic Halides in Aqueous Solution
Lai, Yin-Long,Huang, Jing-Mei
supporting information, p. 2022 - 2025 (2017/04/28)
A new route for the direct cross-coupling of alkyl and allylic halides using electrochemical technique has been developed in aqueous media under air. Catalyzed by Pd(OAc)2, the Zn-mediated allylic alkylations proceed smoothly between a full range of alkyl halides (primary, secondary, and tertiary) and substituted allylic halides. Protection-deprotection of acidic hydrogen in the substrates is avoided.
Direct Reduction of 1-Bromo-6-chlorohexane and 1-Chloro-6-iodohexane at Silver Cathodes in Dimethylformamide
Rose, John A.,McGuire, Caitlyn M.,Hansen, Angela M.,Karty, Jonathan A.,Mubarak, Mohammad S.,Peters, Dennis G.
, p. 311 - 317 (2016/10/05)
Cyclic voltammetry and controlled-potential (bulk) electrolyses have been employed to probe the electrochemical reductions of 1-bromo-6-chlorohexane and 1‐chloro-6-iodohexane at silver cathodes in dimethylformamide (DMF) containing 0.050?M tetra-n-butylammonium tetrafluoroborate (TBABF4). A cyclic voltammogram for reduction of 1-bromo-6-chlorohexane shows a single major irreversible cathodic peak, whereas reduction of 1-chloro-6-iodohexane gives rise to a pair of irreversible cathodic peaks. Controlled-potential (bulk) electrolyses of 1-bromo-6-chlorohexane at a silver gauze cathode reveal that the process involves a two-electron cleavage of the carbon–bromine bond to afford 1-chlorohexane as the major product, along with 6-chloro-1-hexene, n‐hexane, 1‐hexene, and 1,5-hexadiene as minor species. In contrast, bulk electrolyses of 1-chloro-6-iodohexane indicate that the first voltammetric peak corresponds to a one-electron process, leading to production of a dimer (1,12-dichlorododecane) together with 1-chlorohexane and 6-chloro-1-hexene as well as 1‐hexene and 1,5-hexadiene in trace amounts. At potentials corresponding to the second cathodic peak, reduction of 1-chloro-6-iodohexane is a mixture of one- and two-electron steps that yields the same set of products, but in different proportions. Mechanistic schemes are proposed to explain the electrochemical behavior of both 1‐bromo-6-chlorohexane and 1-chloro-6-iodohexane.
Design of Core-Pd/Shell-Ag Nanocomposite Catalyst for Selective Semihydrogenation of Alkynes
Mitsudome, Takato,Urayama, Teppei,Yamazaki, Kenji,Maehara, Yosuke,Yamasaki, Jun,Gohara, Kazutoshi,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
supporting information, p. 666 - 670 (2016/02/18)
We designed core-Pd/shell-Ag nanocomposite catalyst (Pd@Ag) for highly selective semihydrogenation of alkynes. The construction of the core-shell nanocomposite enables a significant improvement in the low activity of Ag NPs for the selective semihydrogenation of alkynes because hydrogen is supplied from the core-Pd NPs to the shell-Ag NPs in a synergistic manner. Simultaneously, coating the core-Pd NPs with shell-Ag NPs results in efficient suppression of overhydrogenation of alkenes by the Pd NPs. This complementary action of core-Pd and shell-Ag provides high chemoselectivity toward a wide range of alkenes with high Z-selectivity under mild reaction conditions (room temperature and 1 atm H2). Moreover, Pd@Ag can be easily separated from the reaction mixture and is reusable without loss of catalytic activity or selectivity.
