1460-02-2Relevant academic research and scientific papers
Carbon dioxide promoted palladium-catalyzed cyclotrimerization of alkynes in water
Li, Jin-Heng,Xie, Ye-Xiang
, p. 1737 - 1743 (2004)
In water, CO2 was found to promote the palladium-catalyzed cyclotrimerization of alkynes. In the presence of PdCl2, CuCl 2, and CO2, both aryl and alkylalkynes afforded the corresponding cyclotrimerization products regioselectively in high yields. However, tert-butylacetylene bearing a bulk group gave a dimerization product.
Stereoselective hydrodehalogenation via a radical-based mechanism involving T-shaped chiral nickel(I) pincer complexes
Rettenmeier, Christoph,Wadepohl, Hubert,Gade, Lutz H.
, p. 9657 - 9665 (2014)
We herein report the catalytic enantioselective hydrodehalogenation based on the interplay of a chiral molecular nickel(I)/nickel(II)hydride system. Prochiral geminal dihalogenides are dehalogenated via a secondary configurationally unstable, potentially metal-stabilized radical intermediate. In a subsequent step, the liberated radical is then trapped by the nickel(II) hydrido complex, present in a large excess under the catalytic conditions, which in turn induces the enantioselectivity during the hydrogen atom transfer onto the radical intermediate. These new chiral nickel(I) complexes were found to catalyze the asymmetric hydrodehalogenation of geminal dihalogenides with moderate to good enantiomeric excess values using LiEt3BH as reductant. The main side product generally observed is the dehalogenated alkene, whereas the hydrodehalogenation of the chiral monohalogen compound occurred much more slowly despite the large excess of reductant. Take and give: A chiral molecular nickel(I)/nickel(II)hydride system transforms prochiral geminal dihalogenides in a catalytic hydrodehalogenation to secondary organohalides. Abstraction of a halogen atom by the nickel(I) species generates an organoradical, possibly in rapid equilibrium with a metal-stabilized form, which is enantioselectively reduced by the hydrido nickel complex (see scheme).
Synthesis, crystal structure, and nonlinear optical behavior of β-unsubstituted meso-meso E-vinylene-linked porphyrin dimers
Frampton, Michael J.,Akdas, Huriye,Cowley, Andrew R.,Rogers, Joy E.,Slagle, Jonathan E.,Fleitz, Paul A.,Drobizhev, Mikhail,Rebane, Aleksander,Anderson, Harry L.
, p. 5365 - 5368 (2005)
(Chemical Equation Presented) A vinylene-linked porphyrin dimer, with no substituents at the β-positions, has been synthesized by CuI/CsF promoted Stille coupling. In the crystal structure of this dimer, the C2H 2 bridge is twisted by 45° relative to the plane of the porphyrins. The absorption, emission spectra, and electrochemistry reveal substantial porphyrin-porphyrin π-conjugation. The triplet excited-state absorption spectrum of this dimer makes it suitable for reverse saturable absorption at 710-900 nm.
Cyclotrimerization of alkynes using a multicatalytic system, Pd(II)/chlorohydroquinone/NPMoV, under dioxygen
Yokota, Takahiro,Sakurai, Yasunori,Sakaguchi, Satoshi,Ishii, Yasutaka
, p. 3923 - 3926 (1997)
Cyclotrimerization of internal and terminal alkynes was performed using a new triple catalytic system, Pd(II)/chlorohydroquinone/NPMoV, under atmospheric oxygen. Internal alkynes such as 3-hexyne and 4-octyne were converted into hexaethyl- and hexapropylbenzenes in quantitative yields. Terminal alkyne, t-butylacetylene, afforded 1,3,5-tri-t-butylbenzene without formation of unsymmetrical tri-t-butylbenzenes. The reaction did not take place in the absence of oxygen.
Benzene ring assembly promoted by a camphor derived palladium complex
Carvalho, M. Fernanda N.N.,Almeida, Fernanda M.T.,Galv?o, Adelino M.,Pombeiro, Armando J.L.
, p. 143 - 147 (2003)
Trans -[PdCl2L2] (1, L=3-NNMe2 C10H14O), under mild reaction conditions, acts as a catalyst for the cyclic trimerization of alkynes. The best performance is achieved for the reaction with PhC≡CMe that affords 1,3,5-trimethyl-2,4,6-triphenyl benzene with high activity and selectivity (ca. 99%). As a general trend the catalytic activity is higher for internal (PhC≡CMe, PhC≡CPh) than for terminal alkynes (HC≡CPh, HC≡CtBu, HC≡CCO2Me). Under more drastic experimental conditions the reaction of 1 with PhC≡CPh yields trans-[PdCl2(PhC≡CPh)2] and no catalytic activity is observed. The molecular structure of 1,3,5-trimethyl-2,4,6-triphenyl benzene was confirmed by X-ray diffraction analysis. The molecules were characterized by 1H- and 13C-NMR spectroscopies, FAB-MS and, in some cases, elemental analyses.
Surprising Reactivity of Very Crowded Phosphinic Derivatives
Baceiredo, Antoine,Bertrand, Guy,Mazerolles, Pierre,Majoral, Jean-Pierre
, p. 1197 - 1198 (1981)
An example of intramolecular cyclisation of a crowded phosphinic chloride via loss of hydrogen chloride and formation of a phosphorus-carbon bond is described; unexpected cleavage of an acyclic phosphorus-carbon bond is also reported.
Small molecular neutral microcrystalline iridium(III) complexes as promising molecular oxygen sensors
Li, Ming,Zheng, Baozhan,Luo, Daibing,Sun, Huiqin,Wang, Ning,Huang, Yan,Dai, Jun,Xiao, Dan,Su, Shi-Jian,Lu, Zhiyun
, p. 1926 - 1929 (2015)
Small molecular neutral Ir(iii) complexes have been demonstrated to be promising self-inclusive microcrystalline thin-film oxygen sensors with relatively high sensitivity (Ksv = 6.41), good stability, and linear Stern-Volmer behavior (R2 = 0.9979).
Reversible Cleavage/Formation of the Chromium–Chromium Quintuple Bond in the Highly Regioselective Alkyne Cyclotrimerization
Huang, Yu-Siang,Huang, Gou-Tao,Liu, Yao-Lun,Yu, Jen-Shiang K.,Tsai, Yi-Chou
, p. 15427 - 15431 (2017)
Herein we report the employment of the quintuply bonded dichromium amidinates [Cr{κ2-HC(N-2,6-iPr2C6H3)(N-2,6-R2C6H3)}]2 (R=iPr (1), Me (7)) as catalysts to mediate the [2+2+2] cyclotrimerization of terminal alkynes giving 1,3,5-trisubstituted benzenes. During the catalysis, the ultrashort Cr?Cr quintuple bond underwent reversible cleavage/formation, corroborated by the characterization of two inverted arene sandwich dichromium complexes (μ-η6:η6-1,3,5-(Me3Si)3C6H3)[Cr{κ2-HC(N-2,6-iPr2C6H3)(N-2,6-R2C6H3)}]2 (R=iPr (5), Me (8)). In the presence of σ donors, such as THF and 2,4,6-Me3C6H2CN, the bridging arene 1,3,5-(Me3Si)3C6H3 in 5 and 8 was extruded and 1 and 7 were regenerated. Theoretical calculations were employed to disclose the reaction pathways of these highly regioselective [2+2+2] cylcotrimerization reactions of terminal alkynes.
Synthesis and Structures of Bis(indolyl)-Coordinated Titanium Dichlorido Complexes and Their Catalytic Application in the Cyclotrimerization of Alkynes
Itoh, Keigo,Miura, Narumi,Miyamoto, Ryo,Ohta, Shun,Okazaki, Masaaki,Saitoh, Keiichiro,Satoh, Sora
, p. 2826 - 2835 (2021/09/02)
The impact of the terminal ligands on the titanium center on the coordination features of deprotonated 2,2′-bis(indolyl)methanes (henceforth: bis(indolyl)s) was studied via a structural comparison between {bis(indolyl)}Ti(NEt2)2 complexes and the corresponding dichlorido complexes. As a result, several flexible aspects of bis(indolyl) coordination were found. For example, it was revealed that an η1-coordinated indolyl moiety can change its coordination mode to coordination via the five-membered ring of indolyl when the terminal diethylamido ligands are replaced by chlorido ligands. Moreover, we found that the methoxy group in the central aromatic ring of the bis(indolyl) ligand can coordinate to the titanium center. The synthesized dichlorido complexes were applied for catalytic alkyne cyclotrimerization reactions, as Ti-based catalyst systems are less developed than Co-, Ni-, Ru-, Rh-, and Ir-based systems. During this study, the cyclotrimerization of HCCSiMe3 was found to preferentially produce the 1,3,5-form (1,3,5-form:1,2,4-form = 79:21), contrary to the typical trend of transition-metal-mediated alkyne cyclotrimerization, and the isolated yield (72%) is the highest among the known 1,3,5-favoring reactions using Ti-based catalyst systems. Furthermore, the reaction mechanism was experimentally verified to proceed through a typical stepwise mechanism involving monomeric species.
Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers
Shon, Jong-Hwa,Kim, Dooyoung,Rathnayake, Manjula D.,Sittel, Steven,Weaver, Jimmie,Teets, Thomas S.
, p. 4069 - 4078 (2021/04/06)
Photoredox catalysis has emerged as a powerful strategy in synthetic organic chemistry, but substrates that are difficult to reduce either require complex reaction conditions or are not amenable at all to photoredox transformations. In this work, we show that strong bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands enable high-yielding photoredox transformations of challenging substrates with very simple reaction conditions that require only a single sacrificial reagent. Using blue or green visible-light activation we demonstrate a variety of reactions, which include hydrodehalogenation, cyclization, intramolecular radical addition, and prenylationviaradical-mediated pathways, with optimized conditions that only require the photocatalyst and a sacrificial reductant/hydrogen atom donor. Many of these reactions involve organobromide and organochloride substrates which in the past have had limited utility in photoredox catalysis. This work paves the way for the continued expansion of the substrate scope in photoredox catalysis.
