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1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(8):2054-2057
The enantioselective 1,2‐reduction of α,β‐unsaturated ketones was achieved using a NiH catalyst in the presence of pinacolborane. This mild process represents a general method to access a wide variety of structurally diverse α‐chiral allylic alcohols in excellent yields and enantioselectivity, as well as very high levels of ambidoselectivity for 1,2‐ over 1,4‐reduction. Furthermore, for reactions on a 10 mmol scale, catalyst loadings as low as 0.5 mol % could be employed to deliver product without any detrimental effect on the yield, enantio‐, or ambidoselectivity. 相似文献
2.
Dr. Ikuo Sasaki Jumpei Taguchi Hana Doi Prof. Dr. Hajime Ito Dr. Tatsuo Ishiyama 《化学:亚洲杂志》2016,11(9):1400-1405
A new process has been developed for the iridium(I)‐catalyzed vinylic C?H borylation of α,β‐unsaturated esters with bis(pinacolato)diboron (B2pin2). These reactions proceeded in octane at temperatures in the range of 80–120 °C to afford the corresponding alkenylboronic compounds in high yields with excellent regio‐ and stereoselectivities. The presence of an aryl ester led to significant improvements in the yields of the acyclic alkenylboronates. Crossover experiments involving deuterated substrates as well as a mixture of stereoisomers confirmed that this reaction proceeds via a 1,4‐addition/β‐hydride elimination mechanism. Notably, this reaction was also used to develop a one‐pot borylation/Suzuki–Miyaura cross‐coupling procedure. 相似文献
3.
The newly synthesized 2‐(alk‐3‐en‐1‐ynyl)cyclohex‐2‐enones 4 undergo photodimerization (chemo‐ and regio‐)selectively at the exocyclic C?C bond to give diastereoisomeric mixtures of 1,2‐dialkynyl‐1,2‐dimethylcyclobutanes. On irradiation of 4 in the presence of 2‐chloroacrylonitrile, cyclobutane formation occurs again (chemo‐ and regio‐)selectively at the exocyclic C?C bond to afford diastereoisomeric mixtures of 2‐alkynyl‐1‐chloro‐2‐methylcyclobutanecarbonitriles. Similarly, compounds 4 undergo photoaddition to 2,3‐dimethylbuta‐1,3‐diene exclusively at the exocyclic C?C bond to afford mixtures of [2+2] and [4+2] cycloadducts. 相似文献
4.
Guangcan Xu Sbastien Leloux Pinglu Zhang Jorge Meijide Surez Yongmin Zhang Etienne Derat Mickaël Mnand Olivia Bistri‐Aslanoff Sylvain Roland Tom Leyssens Olivier Riant Matthieu Sollogoub 《Angewandte Chemie (International ed. in English)》2020,59(19):7591-7597
The encapsulation of copper inside a cyclodextrin capped with an N‐heterocyclic carbene (ICyD) allowed both to catch the elusive monomeric (L)CuH and a cavity‐controlled chemoselective copper‐catalyzed hydrosilylation of α,β‐unsaturated ketones. Remarkably, (α‐ICyD)CuCl promoted the 1,2‐addition exclusively, while (β‐ICyD)CuCl produced the fully reduced product. The chemoselectivity is controlled by the size of the cavity and weak interactions between the substrate and internal C?H bonds of the cyclodextrin. 相似文献
5.
Michael Z. Liang Simon J. Meek 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14372-14377
A catalytic enantioselective method for the synthesis of 1,4‐keto‐alkenylboronate esters by a rhodium‐catalyzed conjugate addition pathway is disclosed. A variety of novel, bench‐stable alkenyl gem‐diboronate esters are synthesized. These easily accessible reagents react smoothly with a collection of cyclic α,β‐unsaturated ketones, generating a new C?C bond and stereocenter. Products are isolated in up to 99 % yield with greater than 20:1 E/Z and greater than 99:1 e.r. Mechanistic studies show the site‐selectivity of transmetalation and reactivity is ligand dependent. The utility of the approach is highlighted by gram‐scale synthesis of enantioenriched cyclic 1,4‐diketones, and stereoselective transformations of the products by hydrogenation, allylation, and isomerization. 相似文献
6.
Lillian V. A. Hale N. Marianne Sikes Nathaniel K. Szymczak 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8619-8623
We present an atom‐economic strategy to catalytically generate and intercept nitrile anion equivalents using hydrogen transfer catalysis. Addition of α,β‐unsaturated nitriles to a pincer‐based Ru?H complex affords structurally characterized κ‐N‐coordinated keteniminates by selective 1,4‐hydride transfer. When generated in situ under catalytic hydrogenation conditions, electrophilic addition to the keteniminate was achieved using anhydrides to provide α‐cyanoacetates in high yields. This work represents a new application of hydrogen transfer catalysis using α,β‐unsaturated nitriles for reductive C?C coupling reactions. 相似文献
7.
Guodong Zhang Zhiyong Hu Florian Belitz Yang Ou Nico Pirkl Lukas J. Gooßen 《Angewandte Chemie (International ed. in English)》2019,58(19):6435-6439
In the presence of a [Cp*RhCl2]2 catalyst, the Lewis acid In(OTf)3, and the mild base Na2CO3, aromatic carboxylates and α,β‐unsaturated ketones undergo a unique hydroarylation/Claisen/retro‐Claisen process to give the corresponding indanones. In this carboxylate‐directed ortho‐C?H annelation, the C?COR bond of the ketone and the CO?OH group of the aromatic carboxylate are cleaved, and the hydroxy group is transferred from the aromatic to the aliphatic acyl residue. This reactivity is synthetically useful, particularly when starting from cyclic ketones, which are converted into indanones bearing aliphatic carboxylate side chains, thus greatly increasing the molecular complexity of aromatic carboxylates in a single step. 相似文献
8.
The development of efficient methods for stereocontrolled synthesis of polyol derivatives has been of continuing interest for the synthetic community. We describe herein tandem olefin cross‐metathesis/hemiacetalization/intramolecular oxa‐Michael addition of allylic/homoallylic alcohols, α,β‐unsaturated ketones, and aldehydes, which enabled the synthesis of syn‐1,2‐ and syn‐1,3‐diol derivatives in a step‐economical manner. A series of differentially protected polyol derivatives could be obtained in subsequent transformations via chemoselective/regioselective cleavage of the acetal moiety of the tandem reaction products. 相似文献
9.
Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes,Ketones, α,β‐Unsaturated Esters,and Imines
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Dr. Tsuyoshi Mita Keisuke Saito Masumi Sugawara Prof. Dr. Yoshihiro Sato 《化学:亚洲杂志》2016,11(10):1528-1531
Enantioenriched N‐tert‐butylsulfonyl‐α‐amido silanes were successfully reacted with aldehydes, ketones, imines, and α,β‐unsaturated esters in the presence of a sub‐stoichiometric amount of CsF (0.5 equiv) in 1,2‐dimethoxyethane (DME) at ?20 °C to afford the corresponding coupling products with up to 89 % enantiospecificity in a retentive manner. 相似文献
10.
Diastereocontrolled Monoprotodeboronation of β‐Sulfinimido gem‐Bis(boronates): A General and Stereoselective Route to α,β‐Disubstituted β‐Aminoalkylboronates
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Xiangyu Li Prof. Dr. Dennis G. Hall 《Angewandte Chemie (International ed. in English)》2018,57(32):10304-10308
β‐Aminoalkylboronic acids are bioisosteres of the pharmaceutically important class of β‐amino acids but few stereoselective methods exist for their preparation. The 1,2‐addition of lithiated 1,1‐diborylalkanes onto chiral N‐tert‐butanesulfinyl aldimines produces β‐sulfinimido gem‐bis(boronates) in good to excellent yields with high diastereoselectivity. The optimized conditions involve the use of rubidium fluoride and water, and are compatible with functionalized alkyl, aryl, alkenyl, and alkynyl substituents. Under these conditions, the geminal quaternary alkyl bis(pinacolatoboryl) intermediates undergo a highly diastereoselective monoprotodeboronation to afford a wide range of syn‐α,β‐disubstituted β‐aminoalkylboronates. This novel application of protodeboronation chemistry was shown to result from a kinetically controlled, diastereotopic‐group‐selective B?C bond protolysis dictated by the configuration of the adjacent stereogenic C?N center. Facile acidic cleavage of the sulfinimide auxiliary produces the free aminoboronates with high enantiomeric purity. 相似文献
11.
Mutsumi Sada Dr. Taniyuki Furuyama Dr. Shinsuke Komagawa Prof. Dr. Masanobu Uchiyama Prof. Dr. Seijiro Matsubara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(34):10474-10481
1,4‐Addition of bis(iodozincio)methane to simple α,β‐unsaturated ketones does not proceed well; the reaction is slightly endothermic according to DFT calculations. In the presence of chlorotrimethylsilane, the reaction proceeded efficiently to afford a silyl enol ether of β‐zinciomethyl ketone. The C? Zn bond of the silyl enol ether could be used in a cross‐coupling reaction to form another C? C bond in a one‐pot reaction. In contrast, 1,4‐addition of the dizinc reagent to enones carrying an acyloxy group proceeded very efficiently without any additive. In this case, the product was a 1,3‐diketone, which was generated in a novel tandem reaction. A theoretical/computational study indicates that the whole reaction pathway is exothermic, and that two zinc atoms of bis(iodozincio)methane accelerate each step cooperatively as effective Lewis acids. 相似文献
12.
α‐Aminoxy‐Acid‐Auxiliary‐Enabled Intermolecular Radical γ‐C(sp3)−H Functionalization of Ketones
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Dr. Heng Jiang Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2018,57(6):1692-1696
A method for site‐specific intermolecular γ‐C(sp3)?H functionalization of ketones has been developed using an α‐aminoxy acid auxiliary applying photoredox catalysis. Regioselective activation of an inert C?H bond is achieved by 1,5‐hydrogen atom abstraction by an oxidatively generated iminyl radical. Tertiary and secondary C‐radicals thus formed at the γ‐position of the imine functionality undergo radical conjugate addition to various Michael acceptors to provide, after reduction and imine hydrolysis, the corresponding γ‐functionalized ketones. 相似文献
13.
Xu Liu Zhaobin Han Zheng Wang Kuiling Ding 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):2009-2013
Optically active medium‐sized cyclic carbonyl compounds bearing an α‐chiral carbon center are of interest in pharmaceutical sciences and asymmetric synthesis. Herein, SpinPhox/IrI catalysts have been demonstrated to be highly enantioselective in the asymmetric hydrogenation of the CC bonds in the exocyclic α,β‐unsaturated cyclic carbonyls, including a broad range of α‐alkylidene lactams, unsaturated cyclic ketones, and lactones. It is noteworthy that the procedure can be successfully used in the asymmetric hydrogenation of the challenging α‐alkylidenelactam substrates with six‐ or seven‐membered rings, thus affording the corresponding optically active carbonyl compounds with an α‐chiral carbon center in generally excellent enantiomeric excesses (up to 98 % ee). Synthetic utility of the protocol has also been demonstrated in the asymmetric synthesis of the anti‐inflammatory drug loxoprofen and its analogue, as well as biologically important ε‐aminocaproic acid derivatives. 相似文献
14.
Erika N. Daley Christopher M. Vogels Dr. Stephen J. Geier Dr. Andreas Decken Dr. Simon Doherty Prof. Dr. Stephen A. Westcott 《Angewandte Chemie (International ed. in English)》2015,54(7):2121-2125
The synthesis of phosphinoboronate esters containing a single P? B bond is reported, together with preliminary reactivity studies towards a range of organic substrates. These compounds add readily to aldehydes, ketones, aldimines, and α,β‐unsaturated enones to give primarily the corresponding 1,2‐addition products containing a new P? C bond. The first examples of transition‐metal‐catalyzed phosphinoborations of C‐C multiple bonds in which P? C and B? C bonds are formed in a single step are also disclosed; allenes react by a highly regioselective 1,2‐addition whereas terminal alkynes undergo a formal 1,1‐addition. 相似文献
15.
Dachang Bai Yanjiang Yu Haiming Guo Junbiao Chang Xingwei Li 《Angewandte Chemie (International ed. in English)》2020,59(7):2740-2744
Ni0‐catalyzed chemo‐ and enantioselective [3+2] cycloaddition of cyclopropenones and α,β‐unsaturated ketones/imines is described. This reaction integrates C?C bond cleavage of cyclopropenones and enantioselective functionalization by carbonyl/imine group, offering a mild approach to γ‐alkenyl butenolides and lactams in excellent enantioselectivity (88–98 % ee) through intermolecular C?C activation. 相似文献
16.
Hannelore Goossens Nicola Piens Dr. Saron Catak Prof. Dr. Michel Waroquier Prof. Dr. Karl W. Törnroos Prof. Dr. Veronique Van Speybroeck Prof. Dr. Matthias D'hooghe Prof. Dr. Norbert De Kimpe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3383-3396
The reactivity of 3‐hydroxy‐4‐(1,2‐dihydroxyethyl)‐β‐lactams with regard to the oxidant sodium periodate was evaluated, unexpectedly resulting in the exclusive formation of new 2‐hydroxy‐1,4‐oxazin‐3‐ones through a C3? C4 bond cleavage of the intermediate 4‐formyl‐3‐hydroxy‐β‐lactams followed by a ring expansion. This peculiar transformation stands in sharp contrast with the known NaIO4‐mediated oxidation of 3‐alkoxy‐ and 3‐phenoxy‐4‐(1,2‐dihydroxyethyl)‐β‐lactams, which exclusively leads to the corresponding 4‐formyl‐β‐lactams without a subsequent ring enlargement. In addition, this new class of functionalized oxazin‐3‐ones was further evaluated for its potential use as building blocks in the synthesis of a variety of differently substituted oxazin‐3‐ones, morpholin‐3‐ones and pyrazinones. Furthermore, additional insights into the mechanism and the factors governing this new ring‐expansion reaction were provided by means of density functional theory calculations. 相似文献
17.
1,4‐Iron Migration for Expedient Allene Annulations through Iron‐Catalyzed C−H/N−H/C−O/C−H Functionalizations
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Jiayu Mo Thomas Müller Dr. João C. A. Oliveira Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2018,57(26):7719-7723
C?H activation bears great potential for enabling sustainable molecular syntheses in a step‐ and atom‐economical manner, with major advances having been realized with precious 4d and 5d transition metals. In contrast, we employed earth abundant, nontoxic iron catalysts for versatile allene annulations through a unique C?H/N?H/C?O/C?H functionalization sequence. The powerful iron catalysis occurred under external‐oxidant‐free conditions even at room temperature, while detailed mechanistic studies revealed an unprecedented 1,4‐iron migration regime for facile C?H activations. 相似文献
18.
Metal‐Free CN‐ and NN‐Bond Formation: Synthesis of 1,2,3‐Triazoles from Ketones,N‐Tosylhydrazines,and Amines in One Pot
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Zhengkai Chen Qiangqiang Yan Zhanxiang Liu Prof. Dr. Yuhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17635-17639
A novel synthetic approach toward 1,4‐disubstituted 1,2,3‐triazoles by C?N‐ and N?N‐bond formation has been established under transition‐metal‐free conditions. Complete control of the regioselectivity was successfully achieved. Commercially available anilines, ketones, and N‐tosylhydrazine were treated with molecular iodine in one pot to allow the regioselective generation of 1,4‐disubstituted 1,2,3‐triazoles in high yields without the use of azides. 相似文献
19.
Copper‐Catalyzed Tandem Hydrocupration and Diastereo‐ and Enantioselective Borylalkyl Addition to Aldehydes
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Won Jun Jang Prof. Jaesook Yun 《Angewandte Chemie (International ed. in English)》2018,57(37):12116-12120
We report the copper‐catalyzed stereoselective addition of in situ generated chiral boron‐α‐alkyl intermediates to various aldehydes including α,β‐unsaturated aldehydes under mild conditions. This tandem and multicomponent method facilitated the synthesis of enantiomerically enriched 1,2‐hydroxyboronates bearing contiguous stereocenters in good yield with high diastereo‐ and enantioselectivity up to a ratio greater than 98:2. In particular, α,β‐unsaturated aldehydes were successfully used as electrophiles in Cu?H catalysis through 1,2‐addition without significant reduction. The resulting 1,2‐hydroxyboronates were used in various transformations. 相似文献