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1.
Development of an Enyne Metathesis/Isomerization/Diels–Alder One‐Pot Reaction for the Synthesis of a Novel Near‐Infrared (NIR) Dye Core
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Kohei Yamashita Yuki Fujii Shohei Yoshioka Dr. Hiroshi Aoyama Dr. Hirofumi Tsujino Prof. Dr. Tadayuki Uno Prof. Dr. Hiromichi Fujioka Dr. Mitsuhiro Arisawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17491-17494
N‐Alkyl‐N‐allyl‐2‐alkynylaniline derivatives undergo a tandem ring‐closing enyne metathesis/isomerization/Diels–Alder cycloaddition sequence in the presence of a second‐generation Grubbs catalyst and dienophiles. In practice, the acyclic enyne in the presence of the ruthenium alkylidene first undergoes ring‐closing metathesis to generate cyclic 4‐vinyl‐1,2‐dihydroquinolines; following diene isomerization and then the addition of a dienophile, these ring‐closing metathesis products are selectively converted into a 7‐methyl‐4H‐naphtho[3,2,1‐de]quinoline‐8,11‐dione core. Overall, the reaction sequence converts simple aniline derivatives into π‐conjugated small molecules, which have characteristic absorption in the near‐infrared region, in a single operation through three unique ruthenium‐catalyzed transformations. 相似文献
2.
Palladium‐Catalyzed CH Activation of N‐Allyl Imines: Regioselective Allylic Alkylations to Deliver Substituted Aza‐1,3‐Dienes
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Prof. Dr. Barry M. Trost Dr. Subham Mahapatra Dr. Martin Hansen 《Angewandte Chemie (International ed. in English)》2015,54(20):6032-6036
A new mode of activation of an imine via a rare aza‐substituted π‐allyl complex is described. Palladium‐catalyzed C(sp3)? H activation of the N‐allyl imine and the subsequent nucleophilic attack by the α‐alkyl cyanoester produced the 1‐aza‐1,3‐diene as the sole regioisomer. In contrast, nucleophilic attack by the α‐aryl cyanoester exclusively delivered the 2‐aza‐1,3‐diene, which was employed in an inverse‐electron‐demand Diels–Alder reaction for heterobiaryl synthesis. 相似文献
3.
An Unexpected Double Diels–Alder Reaction of (E)‐2‐Bromo‐4‐aryl‐1,3‐pentadiene Involving [1,5]‐Hydrogen Migration and HBr Elimination: Synthesis of Bicyclo[2.2.2]octene Derivatives
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An unexpected double Diels–Alder (DDA) reaction of (E)‐2‐bromo‐4‐aryl‐1,3‐pentadiene was developed and resulted in a series of “butterfly‐like” bicyclo[2.2.2]octene derivatives in moderate to good yields without the need for a metal catalyst. The proposed mechanism involves a [1,5]‐sigmatropic hydrogen migration and HBr elimination. Through this decisive [1,5]‐hydrogen shift step, the electronic properties and steric hindrance of the conjugated diene substrate are completely altered and the DDA reaction of this potential diene synthon is successfully achieved. 相似文献
4.
Bioinspired Intramolecular Diels–Alder Reaction: A Rapid Access to the Highly‐Strained Cyclopropane‐Fused Polycyclic Skeleton
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Prof. Dr. Shifa Zhu Zhengjiang Guo Zhipeng Huang Prof. Dr. Huanfeng Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2425-2430
A bioinsipred gold‐catalyzed tandem Diels–Alder/Diels–Alder reaction of an enynal and a 1,3‐diene, forming the highly‐strained benzotricyclo[3.2.1.02,7]octane skeleton, was reported. In contrast, a Diels–Alder/Friedel–Crafts tandem reaction occurred instead when silver salts were used as the catalyst. Although both reactions experienced the similar Diels–Alder reaction of a pyrylium intermediate with a 1,3‐diene, they have different reaction mechanisms. The former proceeded with a stepwise Diels–Alder reaction, while the latter one with a concerted one. 相似文献
5.
On treatment with the catalyst InBr3, 1,1‐difluoroallenes that bear a cyclopentene moiety and an aryl group underwent domino ring assembly in the presence or absence of N‐bromosuccinimide or N‐iodosuccinimide to afford aryne precursors such as three‐ringed ortho‐fluoro(halo)phenanthrenes, four‐ringed ortho‐fluoro(halo)tetraphenes, ortho‐fluoro(halo)chrysenes and fluoro[4]helicenes. Metalation of the aryne precursors followed by elimination of the fluoride resulted in the unprecedented systematic generation of arynes bearing π‐extended systems. Diels?Alder reactions of these arynes with isobenzofurans afforded the corresponding cycloadducts whose reductive aromatisation in an SnCl2/HBr system furnished fully aromatised benzotriphenylenes. In addition, oxidative aryl?aryl coupling (the Scholl reaction) of these benzotriphenylenes facilitated the synthesis of ‘half HBCs’ (hexabenzocoronenes). 相似文献
6.
Miguel Peña‐López M. Montserrat Martínez Dr. Luis A. Sarandeses Prof. Dr. José Pérez Sestelo Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(4):910-916
The first total synthesis of (+)‐neomarinone has been achieved by following a concise and convergent route using methyl (R)‐lactate and (R)‐3‐methylcyclohexanone as chiral building blocks. Key steps of the synthesis are the stereocontrolled formation of the two quaternary stereocenters by diastereoselective 1,4‐conjugate addition and enolate alkylation reactions, and the construction of the furanonaphthoquinone skeleton by regioselective Diels–Alder reaction between a 1,3‐bis(trimethylsilyloxy)‐1,3‐diene and a bromoquinone. The synthesis proves the relative and absolute stereochemistry of natural neomarinone. 相似文献
7.
《化学:亚洲杂志》2017,12(18):2399-2403
An intramolecular exo ‐hydroarylation of 2‐aryloxy‐1,4‐disilylbut‐1‐en‐3‐ynes via ortho ‐C−H bond activation under palladium(0) and acid catalysis was found to give 2,3‐bis(silylmethylidene)‐2,3‐dihydrobenzofurans. The two silyl groups present probably promoted the reaction and played a key role in stabilizing the diene moiety in the product. The products readily led to functionalized condensed cycles by a Diels–Alder reaction. 相似文献
8.
Radical copolymerization of N‐phenylmaleimide and diene monomers in competition with diels–alder reaction
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Akikazu Matsumoto Daisuke Yamamoto 《Journal of polymer science. Part A, Polymer chemistry》2016,54(22):3616-3625
Radical copolymerization of N‐phenylmaleimide (PhMI) is carried out with various diene monomers including naturally occurring compounds and the copolymers are efficiently produced by the suppression of Diels–Alder reaction as the competitive side reaction. Diene monomers with an exomethylene moiety and a fixed s‐trans diene structure, such as 3‐methylenecyclopentene and 4‐isopropyl‐1‐methyl‐3‐methylenecyclohexene, exhibit high copolymerization reactivity to produce a high‐molecular‐weight copolymer in a high yield. The copolymerization of sterically hindered noncyclic diene monomers, such as 2,4‐dimethyl‐1,3‐pentadiene and 2,4‐hexadiene, also results in the formation of a high‐molecular‐weight copolymer in a moderate yield. The NMR spectroscopy reveals that the obtained copolymers consist of predominant 1,4‐repeating structures for the corresponding diene unit. The copolymers have excellent thermal stability, that is, an onset temperature of decomposition over 330 °C and a glass transition temperature over 130 °C. The copolymerization reactivity of these diene monomers is discussed based on the results of the DFT calculations. The efficient copolymer formation in competition with Diels–Alder addition is investigated under various conditions of the temperature, solvents, and initiators used for the copolymerization. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3616–3625. 相似文献
9.
Yu‐Rong Chen Annavareddi Naresh Suh‐Yuen Liang Chun‐Hung Lin Rong‐Jie Chein Hsiao‐Ching Lin 《Angewandte Chemie (International ed. in English)》2020,59(32):13537-13541
The 1,3‐enyne moiety is commonly found in cyclohexanoid natural products produced by endophytic and plant pathogenic fungi. Asperpentyn ( 1 ) is a 1,3‐enyne‐containing cyclohexanoid terpenoid isolated from Aspergillus and Pestalotiopsis. The genetic basis and biochemical mechanism of 1,3‐enyne biosynthesis in 1 , and other natural products containing this motif, has remained enigmatic despite their potential ecological roles. Identified here is the biosynthetic gene cluster and characterization of two crucial enzymes in the biosynthesis of 1 . A P450 monooxygenase that has a dual function, to first catalyze dehydrogenation of the prenyl chain to generate a cis‐diene intermediate and then serve as an acetylenase to yield an alkyne moiety, and thus the 1,3‐enyne, was discovered. A UbiA prenyltransferase was also characterized and it is unusual in that it favors transferring a five‐carbon prenyl chain, rather than a polyprenyl chain, to a p‐hydroxybenzoic acid acceptor. 相似文献
10.
Dr. Tao Yang Dr. Beni B. Dangi Aaron M. Thomas Dr. Bing‐Jian Sun Tzu‐Jung Chou Prof. Dr. Agnes H. H. Chang Prof. Dr. Ralf I. Kaiser 《Angewandte Chemie (International ed. in English)》2016,55(28):7983-7987
Silole (1‐silacyclopenta‐2,4‐diene) was synthesized for the first time by the bimolecular reaction of the simplest silicon‐bearing radical, silylidyne (SiH), with 1,3‐butadiene (C4H6) in the gas phase under single‐collision conditions. The absence of consecutive collisions of the primary reaction product prevents successive reactions of the silole by Diels–Alder dimerization, thus enabling the clean gas‐phase synthesis of this hitherto elusive cyclic species from acyclic precursors in a single‐collision event. Our method opens up a versatile and unconventional path to access a previously rather obscure class of organosilicon molecules (substituted siloles), which have been difficult to access through classical synthetic methods. 相似文献
11.
Sulfur‐substituted 4‐quinolizidinones, previously prepared by aza‐Diels‐Alder reactions and ring‐closing metathesis, are now subjected to further synthetic transformations. Formal synthesis of cermizine C and 5‐epi‐cermizine C, and some other useful reactions have been achieved. 相似文献
12.
Barry M. Trost Subham Mahapatra Martin Hansen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(20):6130-6134
A new mode of activation of an imine via a rare aza‐substituted π‐allyl complex is described. Palladium‐catalyzed C(sp3) H activation of the N‐allyl imine and the subsequent nucleophilic attack by the α‐alkyl cyanoester produced the 1‐aza‐1,3‐diene as the sole regioisomer. In contrast, nucleophilic attack by the α‐aryl cyanoester exclusively delivered the 2‐aza‐1,3‐diene, which was employed in an inverse‐electron‐demand Diels–Alder reaction for heterobiaryl synthesis. 相似文献
13.
Day‐Shin Hsu Prof. Dr. Yu‐Yu Chou Yen‐Shih Tung Chun‐Chen Liao Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(10):3121-3131
An efficient and short entry to polyfunctionalized linear triquinanes from 2‐methoxyphenols is described by utilizing the following chemistry. The Diels–Alder reactions of masked o‐benzoquinones, derived from 2‐methoxyphenols, with cyclopentadiene afford tricyclo[5.2.2.02,6]undeca‐4,10‐dien‐8‐ones. Photochemical oxa‐di‐π‐methane (ODPM) rearrangements and 1,3‐acyl shifts of the Diels–Alder adducts are investigated. The ODPM‐rearranged products are further converted to linear triquinanes by using an O‐stannyl ketyl fragmentation. Application of this efficient strategy to the total synthesis of (±)‐Δ9(12)‐capnellene was accomplished from 2‐methoxy‐4‐methylphenol in nine steps with 20 % overall yield. 相似文献
14.
Zhishan Su Dr. Song Qin Dr. Changwei Hu Prof. Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(14):4359-4367
The mechanism of the hetero‐Diels–Alder reactions of Brassard’s diene and 1,3‐butadiene catalyzed by a titanium(IV) complex of a tridentate Schiff base was investigated by DFT and ONIOM methods. The calculations indicate that the mechanism of the reaction is closely related to the nucleophilicity–electrophilicity between diene and carbonyl substrates. A stepwise pathway is adopted for Brassard’s diene, and the step corresponding to the formation of the C? C bond is predicted to be the rate‐determining step with a free‐energy barrier of 8.4 kcal mol?1. For 1,3‐butadiene, the reaction takes place along a one‐step, two‐stage pathway with a free‐energy barrier of 14.9 kcal mol?1. For Brassard’s diene as substrate, the OCH3 and OSi(CH3)3 substituents may play a key role in the formation of the transition state and zwitterionic intermediate by participating in charge transfer from Brassard’s diene to formaldehyde. The combination of the phenyl groups at the amino alcohol moiety and the ortho‐tert‐butyl group of the salicylaldehyde moiety in the chiral tridentate Schiff base ligand plays an important role in the control of the stereoselectivity, which is in agreement with experimental observations. 相似文献
15.
Triazolyl phenylalanine and tyrosine‐aryl C‐glycoside hybrids were readily synthesized via microwave‐assisted Cu(I)‐catalyzed azide‐alkyne 1,3‐dipolar cycloaddition in high yields. Successive enzymatic assay identified the synthesized glycoconjugates as novel PTP1B inhibitors with low micromole‐ranged inhibitory activity and at least several‐fold selectivity over other homologous PTPs tested. In addition, the benzyl groups on glucosyl moiety were found crucial toward PTP1B inhibition. 相似文献
16.
Three 1,3‐bridged polycyclic cyclopropenes, exo‐8‐oxatricyclo[3.2.1.02,4]octa‐2,6‐diene ( 10 ), endo‐8‐oxatricyclo[3.2.1.02,4]octa‐2,6‐diene ( 11 ), and exo‐6,7‐benzo‐1,5‐diphenyl‐8‐oxatricyclo[3.2.1.02,4]octa‐2,6‐diene ( 12 ), have been synthesized by elimination of 2‐chloro‐3‐trimethylsilyl‐8‐oxatricyclo[3.2.1.02,4]‐oct‐6‐enes, 17 , 18 and 30 , which were generated from 1‐chloro‐3‐trimethylsilylcyclopropene with furan and diphenylisobenzofuran. We have demonstrated a facile route to synthesize the highly strained 1,3‐fused polycyclic cyclopropenes, 10 , 11 , and 12 . The stereochemistry of the Diels‐Alder reactions of cyclopropene 16 with furan and DPIBF are different. Cyclopropene 16 was treated with furan to form exo‐exo and endo‐exo adducts (5:2) and treated with DPIBF to generate an exo‐exo adduct. Compounds 10 , 11 and 12 undergo isomerization reactions to form benzaldehyde and phenyl 4‐phenyl‐[1]naphthyl ketone to release strain energies via diradical mechanisms. 相似文献
17.
Rasheed AhmadKhera Rasheed Ahmad Ihsan Ullah Obaid‐Ur‐Rahman Abid Olumide Fatunsin Muhammad Sher Alexander Villinger Peter Langer 《Helvetica chimica acta》2010,93(9):1705-1715
2‐Aryl‐2,3‐dihydro‐4H‐pyran‐4‐ones were prepared in one step by cyclocondensation of 1,3‐diketone dianions with aldehydes. The use of HCl (10%) for the aqueous workup proved to be very important to avoid elimination reactions of the 5‐aryl‐5‐hydroxy 1,3‐diones formed as intermediates. The TiCl4‐mediated cyclization of a 2‐aryl‐2,3‐dihydro‐4H‐pyran‐4‐one with 1,3‐silyloxybuta‐1,3‐diene resulted in cleavage of the pyranone moiety and formation of a highly functionalized benzene derivative. 相似文献
18.
Non‐coordinating‐Anion‐Directed Reversal of Activation Site: Selective C−H Bond Activation of N‐Aryl Rings
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Prof. Dr. Dawei Wang Xiaoli Yu Prof. Dr. Xiang Xu Bingyang Ge Xiaoli Wang Yaxuan Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8663-8668
An Rh‐catalyzed selective C?H bond activation of diaryl‐substituted anilides is described. In an attempt to achieve C?H activation of C‐aryl rings, we unexpectedly obtained an N‐aryl ring product under non‐coordinating anion conditions, whereas the C‐aryl ring product was obtained in the absence of a non‐coordinating anion. This methodology has proved to be an excellent means of tuning and adjusting selective C?H bond activation of C‐aryl and N‐aryl rings. The approach has been rationalized by mechanistic studies and theoretical calculations. In addition, it has been found and verified that the catalytic activity of the rhodium catalyst is obviously improved by non‐coordinating anions, which provides an efficient strategy for obtaining a highly chemoselective catalyst. Mechanistic experiments also unequivocally ruled out the possibility of a so‐called “silver effect” in this transformation involving silver. 相似文献
19.
Stereoselective Synthesis and Physicochemical Properties of Liquid‐Crystal Compounds Possessing a trans‐2,5‐Disubstituted Tetrahydropyran Ring with Negative Dielectric Anisotropy
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Dr. Keisuke Araki Dr. Tetsuya Yamamoto Dr. Ryoji Tanaka Makoto Ushioda Dr. Yasuyuki Gotoh Dr. Tetsu Yamakawa Dr. Munenori Inoue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2458-2466
Three stereoselective syntheses and the physicochemical properties of trans,trans‐5‐(4‐ethoxy‐2,3‐difluorophenyl)‐2‐(4‐propylcyclohexyl)tetrahydropyran, which is an important liquid‐crystal compound with a large negative dielectric anisotropy (Δε=?7.3), are described. The key step in the construction of the trans‐2,5‐disubstituted tetrahydropyran ring in the first approach involved a benzylic cation mediated intramolecular olefin cyclization of a 2‐allyloxy‐1‐arylethanol derivative. The second method included the Et2Zn‐induced 1,2‐aryl shift of a bromohydrin obtained from a hetero‐Diels–Alder reaction, followed by stereoselective bromination. The third approach utilized the hetero‐Diels–Alder reaction of trans‐4‐propylcyclohexanecarboxaldehyde and a 2‐aryl‐3‐(trimethylsilyl)oxy‐1,3‐butadiene, followed by stereoselective protonation. From results obtained by using a quantum chemical calculation method, the reason why the target compound shows a large negative Δε value is discussed. 相似文献
20.
Base‐Free Conditions for Rhodium‐Catalyzed Asymmetric Arylation To Produce Stereochemically Labile α‐Aryl Ketones
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Dr. Xiaowei Dou Prof. Dr. Yixin Lu Prof. Dr. Tamio Hayashi 《Angewandte Chemie (International ed. in English)》2016,55(23):6739-6743
The asymmetric arylation of 2,2‐dialkyl cyclopent‐4‐ene‐1,3‐diones with aryl boronic acids was found to be efficiently catalyzed by a chiral diene–rhodium μ‐chloro dimer, [{RhCl((R)‐diene*)}2], in the absence of bases in toluene/H2O to give 2,2‐dialkyl 4‐aryl cyclopentane‐1,3‐diones in high yields with high enantioselectivity. Such compounds can not be obtained with high enantiomeric purity under the standard basic conditions used for rhodium‐catalyzed asymmetric arylation because the α‐aryl ketone products undergo racemization under the basic conditions. 相似文献