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1.
Ruthenium‐Catalyzed Cycloisomerization of 2,2′‐Diethynyl‐ biphenyls Involving Cleavage of a Carbon–Carbon Triple Bond 下载免费PDF全文
Prof. Dr. Takanori Matsuda Kotaro Kato Tsuyoshi Goya Shingo Shimada Prof. Dr. Masahiro Murakami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):1941-1943
A ruthenium complex catalyzes a new cycloisomerization reaction of 2,2′‐diethynylbiphenyls to form 9‐ethynylphenanthrenes, thereby cleaving the carbon–carbon triple bond of the original ethynyl group. A metal–vinylidene complex is generated from one of the two ethynyl groups, and its carbon–carbon double bond undergoes a [2+2] cycloaddition with the other ethynyl group to form a cyclobutene. The phenanthrene skeleton is constructed by the subsequent electrocyclic ring opening of the cyclobutene moiety. 相似文献
2.
Proton Order–Disorder Phenomena in a Hydrogen‐Bonded Rhodium–η5‐Semiquinone Complex: A Possible Dielectric Response Mechanism 下载免费PDF全文
Dr. Minoru Mitsumi Kazunari Ezaki Yuuki Komatsu Prof. Dr. Koshiro Toriumi Dr. Tatsuya Miyatou Prof. Dr. Motohiro Mizuno Nobuaki Azuma Prof. Dr. Yuji Miyazaki Prof. Dr. Motohiro Nakano Prof. Dr. Yasutaka Kitagawa Dr. Takayasu Hanashima Dr. Ryoji Kiyanagi Dr. Takashi Ohhara Prof. Dr. Kazuhiro Nakasuji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9682-9696
A newly synthesized one‐dimensional (1D) hydrogen‐bonded (H‐bonded) rhodium(II)–η5‐semiquinone complex, [Cp*Rh(η5‐p‐HSQ‐Me4)]PF6 ([ 1 ]PF6; Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl; HSQ=semiquinone) exhibits a paraelectric–antiferroelectric second‐order phase transition at 237.1 K. Neutron and X‐ray crystal structure analyses reveal that the H‐bonded proton is disordered over two sites in the room‐temperature (RT) phase. The phase transition would arise from this proton disorder together with rotation or libration of the Cp* ring and PF6? ion. The relative permittivity εb′ along the H‐bonded chains reaches relatively high values (ca., 130) in the RT phase. The temperature dependence of 13C CP/MAS NMR spectra demonstrates that the proton is dynamically disordered in the RT phase and that the proton exchange has already occurred in the low‐temperature (LT) phase. Rate constants for the proton exchange are estimated to be 10?4–10?6 s in the temperature range of 240–270 K. DFT calculations predict that the protonation/deprotonation of [ 1 ]+ leads to interesting hapticity changes of the semiquinone ligand accompanied by reduction/oxidation by the π‐bonded rhodium fragment, producing the stable η6‐hydroquinone complex, [Cp*Rh3+(η6‐p‐H2Q‐Me4)]2+ ([ 2 ]2+), and η4‐benzoquinone complex, [Cp*Rh+(η4‐p‐BQ‐Me4)] ([ 3 ]), respectively. Possible mechanisms leading to the dielectric response are discussed on the basis of the migration of the protonic solitons comprising of [ 2 ]2+ and [ 3 ], which would be generated in the H‐bonded chain. 相似文献
3.
Asymmetric Total Synthesis of (−)‐Englerin A through Catalytic Diastereo‐ and Enantioselective Carbonyl Ylide Cycloaddition 下载免费PDF全文
Dr. Taiki Hanari Dr. Naoyuki Shimada Dr. Yasunobu Kurosaki Dr. Neetipalli Thrimurtulu Dr. Hisanori Nambu Dr. Masahiro Anada Prof. Dr. Shunichi Hashimoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11671-11676
An asymmetric total synthesis of the guaiane sesquiterpene (?)‐englerin A, a potent and selective inhibitor of the growth of renal cancer cell lines, was accomplished. The basis of the approach is a highly diastereo‐ and enantioselective carbonyl ylide cycloaddition with an ethyl vinyl ether dipolarophile under catalysis by dirhodium(II) tetrakis[N‐tetrachlorophthaloyl‐(S)‐tert‐leucinate], [Rh2(S‐TCPTTL)4], to construct the oxabicyclo[3.2.1]octane framework with concomitant introduction of the oxygen substituent at C9 on the exo‐face. Another notable feature of the synthesis is ruthenium tetraoxide‐catalyzed chemoselective oxidative conversion of C9 ethyl ether to C9 acetate. 相似文献
4.
Prof. Dr. Azusa Kondoh Prof. Dr. Masahiro Terada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(45):e202201198
A new methodology for the synthesis of 2,2-disubstituted 2H-chromenes was developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. Phosphazene P2-tBu efficiently catalyzed the addition reaction of 4H-chromen-4-ols containing a diethoxyphosphoryl group with α,β-unsaturated ketones, which involved the catalytic generation of a carbanion through the [1,2]-phospha-Brook rearrangement and subsequent conjugate addition at the 2-position to afford adducts possessing an alkenylphosphate moiety in a highly diastereoselective manner. Further transformation of the adducts based on a nickel-catalyzed cross-coupling reaction with arylzinc reagents provided densely functionalized 2,2-disubstituted 2H-chromenes. 相似文献
5.
Prof. Dr. Azusa Kondoh Takayuki Hirozane Prof. Dr. Masahiro Terada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(42):e202201240
The formal enantioselective umpolung addition of dialkyl phosphites to 2-azaaryl ketones was developed under Brønsted base catalysis. The reaction involves the enantioselective protonation of the transient α-oxygenated (2-azaaryl)methyl anion generated through the 1,2-addition of the anion of dialkyl phosphite to the 2-azaaryl ketone and the subsequent [1,2]-phospha-Brook rearrangement. A chiral bis(guanidino)iminophosphorane organosuperbase efficiently catalyzed the reaction to provide enantio-enriched phosphates in high yields with good to high enantioselectivities. This is a rare example of the catalytic enantioselective protonation of transient carbanions other than enolates, constructing a trisubstituted stereogenic center α to 2-azaarenes. 相似文献
6.
Jie Wang Denan Li Honggui Yang Shufan Yao Prof. Qianqian Zhu Prof. Masahiro Sadakane Prof. Yanshuo Li Prof. Wataru Ueda Prof. Zhenxin Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(41):e202200618
Zeolitic octahedral metal oxides are inorganic crystalline microporous materials with adsorption and redox properties. New ϵ-Keggin nickel molybdate–based zeolitic octahedral metal oxides have been synthesized. 31P NMR spectroscopy shows that reduction of MoVI-based molybdates forms an ϵ-Keggin polyoxometalate that immediately transfers to the solid phase. Investigation of the formation process indicates that a low Ni concentration, insoluble reducing agent, and long synthesis time are the critical factors for obtaining the zeolite octahedral metal oxides rather than the ϵ-Keggin polyoxometalate molecule. The synthesized zeolitic nickel molybdate with Na+ is used as the adsorbent, which effectively separates C2 hydrocarbon mixtures. 相似文献
7.
Tairin Kawasaki Naoki Ishida Masahiro Murakami 《Angewandte Chemie (International ed. in English)》2020,59(41):18267-18271
A convenient method is reported to specifically acylate phenolic hydroxyl groups through a radical pathway. When a mixture of an aldehyde and a phenol in ethyl acetate is irradiated with blue light in the presence of iridium and nickel bromide catalysts at ambient temperature, phenoxyl and acyl radicals are transiently generated in situ and cross‐couple to furnish an ester. Aliphatic hydroxy groups remain untouched under the reaction conditions. 相似文献
8.
Optical Review - We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain... 相似文献
9.
Kentarou Sakamoto Dr. Misao Akishiba Takahiro Iwata Dr. Kazuya Murata Dr. Seiya Mizuno Dr. Kenichi Kawano Dr. Miki Imanishi Prof. Dr. Fumihiro Sugiyama Prof. Dr. Shiroh Futaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20165-20173
Endocytic pathways are practical routes for the intracellular delivery of biomacromolecules. Along with this, effective strategies for endosomal cargo release into the cytosol are desired to achieve successful delivery. Focusing on compositional differences between the cell and endosomal membranes and the pH decrease within endosomes, we designed the lipid-sensitive and pH-responsive endosome-lytic peptide HAad. This peptide contains aminoadipic acid (Aad) residues, which serve as a safety catch for preferential permeabilization of endosomal membranes over cell membranes, and His-to-Ala substitutions enhance the endosomolytic activity. The ability of HAad to destabilize endosomal membranes was supported by model studies using large unilamellar vesicles (LUVs) and by increased intracellular delivery of biomacromolecules (including antibodies) into live cells. Cerebral ventricle injection of Cre recombinase with HAad led to Cre/loxP recombination in a mouse model, thus demonstrating potential applicability of HAad in vivo. 相似文献
10.
Dr. Yoji Horii Prof. Dr. Keiichi Katoh Prof. Dr. Yuji Miyazaki Dr. Marko Damjanović Tetsu Sato Prof. Dr. Liviu Ungur Prof. Dr. Liviu F. Chibotaru Prof. Dr. Brian K. Breedlove Prof. Dr. Motohiro Nakano Prof. Dr. Wolfgang Wernsdorfer Prof. Dr. Masahiro Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8076-8082
Gd3+ complexes have been shown to undergo unusual slow magnetic relaxation processes similar to those of single-molecule magnets (SMMs), even though Gd3+ does not exhibit strong magnetic anisotropy. To reveal the origin of the slow magnetic relaxation of Gd3+ complexes, we have investigated the magnetic properties and heat capacities of two Gd3+-phthalocyaninato triple-decker complexes, one of which has intramolecular Gd3+–Gd3+ interactions and the other does not. It was found that the Gd3+–Gd3+ interactions accelerate the magnetic relaxation processes. In addition, magnetically diluted samples, prepared by doping a small amount of the Gd3+ complexes into a large amount of diamagnetic Y3+ complexes, underwent dual magnetic relaxation processes. A detailed dynamic magnetic analysis revealed that the coexistence of spin–lattice relaxation and phonon-bottleneck processes is the origin of the dual magnetic relaxation processes. 相似文献