共查询到20条相似文献,搜索用时 703 毫秒
1.
Ottorino DeLucchi Arif Datan Aliye Altunda Fabrizio Fabris Metin Balci 《Helvetica chimica acta》2004,87(9):2364-2367
An efficient synthetic route to the concave‐shaped, potentially ionophoric syn‐ and anti‐isomers of 5,6,11,12,17,18‐hexahydro‐5,18:6,11:12,17‐triepoxytrinaphthylene ( 4 ) was elaborated. Starting from ‘oxabenzonorbornadiene’ ( 5 ), the stannylated precursor 9 was prepared in three steps, followed by cyclotrimerization catalyzed by copper(I) thiophene‐2‐carboxylate (CuTC) , which afforded 4 in a syn/anti ratio of 5 : 4. 相似文献
2.
K. Geetharani Dr. Samat Tussupbayev Dr. Julia Borowka Prof. Dr. Max C. Holthausen Dr. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(27):8482-8489
The reaction of nido‐[1,2‐(Cp*RuH)2B3H7] ( 1 a , Cp*=η5‐C5Me5) with [Mo(CO)3(CH3CN)3] under mild conditions yields the new metallaborane arachno‐[(Cp*RuCO)2B2H6] ( 2 ). Compound 2 catalyzes the cyclotrimerization of a variety of internal‐ and terminal alkynes to yield mixtures of 1,3,5‐ and 1,2,4‐substituted benzenes. The reactivities of nido‐ 1 a and arachno‐ 2 with alkynes demonstrates that a change in geometry from nido to arachno drives a change in the reaction from alkyne‐insertion to catalytic cyclotrimerization, respectively. Density functional calculations have been used to evaluate the reaction pathways of the cyclotrimerization of alkynes catalyzed by compound 2 . The reaction involves the formation of a ruthenacyclic intermediate and the subsequent alkyne‐insertion step is initiated by a [2+2] cycloaddition between this intermediate and an alkyne. The experimental and quantum‐chemical results also show that the stability of the metallacyclic intermediate is strongly dependent on the nature of the substituents that are present on the alkyne. 相似文献
3.
Dr. Stefano Tartaggia Prof. Ottorino De Lucchi Prof. Andrea Gambaro Dr. Roberta Zangrando Prof. Dr. Fabrizio Fabris Dr. Alessandro Scarso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(18):5701-5714
The synthesis of enantiopure (+)‐benzotricamphor syn‐ 5 , an important chiral C3‐symmetric rigid building block for supramolecular applications, was studied in detail to reduce the number of steps and to increase the diastereoselectivity and overall yield. The new synthetic procedure allowed larger amounts of syn‐ 5 to be obtained and used for the preparation of new derivatives, such as the corresponding tris‐trifluoromethanesulfonate syn‐ 12 , which was efficiently transformed into (+)‐benzotribornenetrinitrile syn‐ 1 and (+)‐benzotribornenetris(ethynyl‐4‐pyridine) syn‐ 2 . The previously reported (+)‐benzotricamphortrioxime syn‐ 6 was transformed into tris‐nitrile syn‐ 3 by Beckman reaction. Compounds syn‐ 1 – 3 were employed as multidentate ligands for silver(I) and platinum(II) centres in apolar solvents. The linear coordination geometry of AgI and square‐planar geometry of cis‐chelated PtII in combination with the chiral tripodal ligands syn‐ 1 – 3 led to the formation of chiral enantiopure capsules with M3L2 stoichiometry, as confirmed by 2D NMR NOESY and DOSY experiments as well as ESI mass spectrometry. 相似文献
4.
A Versatile Synthesis of β‐Lactam‐Fused Oxacycles through the Palladium‐Catalyzed Chemo‐, Regio‐, and Diastereoselective Cyclization of Allenic Diols
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Prof. Dr. Benito Alcaide Dr. Pedro Almendros Dr. Rocío Carrascosa Dr. Luis Casarrubios Dr. Elena Soriano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):2200-2213
Chemo‐, regio‐ and stereocontrolled palladium‐catalyzed preparations of enantiopure morpholines, oxocines, and dioxonines have been developed starting from 2‐azetidinone‐tethered γ,δ‐, δ,ε‐, and ε,ζ‐allendiols. The palladium‐catalyzed cyclizative coupling reaction of γ,δ‐allendiols 2 with allyl bromide or lithium bromide was effective as 8‐endo cyclization by attack of the primary hydroxy group to the terminal allene carbon to afford enantiopure functionalized oxocines; whereas the palladium‐catalyzed cyclizative coupling reaction of 2‐azetidinone‐tethered ε,ζ‐allendiols 4 furnished dioxonines 16 through a totally chemo‐ and regioselective 9‐endo oxycyclization. By contrast, the palladium‐catalyzed cyclizative coupling reaction of 2‐azetidinone‐tethered δ,ε‐allendiols 3 with aryl and alkenyl halides exclusively generated six‐membered‐ring compounds 14 a and 15 a . These results could be explained through a 6‐exo cyclization by chemo‐ and regiospecific attack of the secondary hydroxy group to the internal allene carbon. Chemo‐ and regiocontrol issues are mainly influenced by the length of the tether rather than by the nature of the metal catalysts and substituents. This reactivity can be rationalized by means of density functional theory calculations. 相似文献
5.
Murat Güney Selçuk Eşsiz Arif Daştan Metin Balci Ottorino De Lucchi Ertan Şahin Fabrizio Fabris 《Helvetica chimica acta》2013,96(5):941-950
Stereoisomerically pure endo‐ and exo‐7‐halo‐7‐(trimethylstannyl)benzonorcar‐3‐enes (=endo‐ and exo‐(1‐halo‐1a,2,7,7a‐tetrahydro‐1H‐cyclopropa[b]naphthalen‐1‐yl)trimethylstannane) 4 and 6 were selectively obtained by lithium? tin or magnesium? tin transmetalation in good yields (Scheme 2 and 3). The reaction of these compounds with copper(I) thiophene‐2‐carboxylate (CuTC) produced in both cases the corresponding CS‐symmetric bicyclopropylidene (=cyclopropylidenecyclopropane) syn‐ 1 , a single diastereoisomer (Schemes 5 and 6). The structure of syn‐ 1 was undoubtedly elucidated by X‐ray single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed (Scheme 7). 相似文献
6.
A Concise and Highly Enantioselective Total Synthesis of (+)‐anti‐ and (−)‐syn‐Mefloquine Hydrochloride: Definitive Absolute Stereochemical Assignment of the Mefloquines
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ettore J. Rastelli Prof. Don M. Coltart 《Angewandte Chemie (International ed. in English)》2015,54(47):14070-14074
A concise asymmetric (>99:1 e.r.) total synthesis of (+)‐anti‐ and (?)‐syn‐mefloquine hydrochloride from a common intermediate is described. The key asymmetric transformation is a Sharpless dihydroxylation of an olefin that is accessed in three steps from commercially available materials. The Sharpless‐derived diol is converted into either a trans or cis epoxide, and these are subsequently converted into (+)‐anti‐ and (?)‐syn‐mefloquine, respectively. The synthetic (+)‐anti‐ and (?)‐syn‐mefloquine samples were derivatized with (S)‐(+)‐mandelic acid tert‐butyldimethylsilyl ether, and a crystal structure of each derivative was obtained. These are the first X‐ray structures for mefloquine derivatives that were obtained by coupling to a known chiral, nonracemic compound, and provide definitive confirmation of the absolute stereochemistry of (+)‐anti‐ as well as (?)‐syn‐mefloquine. 相似文献
7.
Binuclear trans‐Bis(β‐iminoaryloxy)palladium(II) Complexes Doubly Linked with Pentamethylene Spacers: Structure‐Dependent Flapping Motion and Heterochiral Association Behavior of the Clothespin‐Shaped Molecules
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Masaya Naito Hiroyuki Souda Hiroshi Koori Dr. Naruyoshi Komiya Prof. Takeshi Naota 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):6991-7000
The synthesis, structure, and solution‐state behavior of clothespin‐shaped binuclear trans‐bis(β‐iminoaryloxy)palladium(II) complexes doubly linked with pentamethylene spacers are described. Achiral syn and racemic anti isomers of complexes 1 – 3 were prepared by treating Pd(OAc)2 with the corresponding N,N′‐bis(β‐hydroxyarylmethylene)‐1,5‐pentanediamine and then subjecting the mixture to chromatographic separation. Optically pure (100 % ee) complexes, (+)‐anti‐ 1 , (+)‐anti‐ 2 , and (+)‐anti‐ 3 , were obtained from the racemic mixture by employing a preparative HPLC system with a chiral column. The trans coordination and clothespin‐shaped structures with syn and anti conformations of these complexes have been unequivocally established by X‐ray diffraction studies. 1H NMR analysis showed that (±)‐anti‐ 1 , (±)‐anti‐ 2 , syn‐ 2 , and (±)‐anti‐ 3 display a flapping motion by consecutive stacking association/dissociation between cofacial coordination planes in [D8]toluene, whereas syn‐ 1 and syn‐ 3 are static under the same conditions. The activation parameters for the flapping motion (ΔH≠ and ΔS≠) were determined from variable‐temperature NMR analyses as 50.4 kJ mol?1 and 60.1 J mol?1 K?1 for (±)‐anti‐ 1 , 31.0 kJ mol?1 and ?22.7 J mol?1 K?1 for (±)‐anti‐ 2 , 29.6 kJ mol?1 and ?57.7 J mol?1 K?1 for syn‐ 2 , and 35.0 kJ mol?1 and 0.5 J mol?1 K?1 for (±)‐anti‐ 3 , respectively. The molecular structure and kinetic parameters demonstrate that all of the anti complexes flap with a twisting motion in [D8]toluene, although (±)‐anti‐ 1 bearing dilated Z‐shaped blades moves more dynamically than I‐shaped (±)‐anti‐ 2 or the smaller (±)‐anti‐ 3 . Highly symmetrical syn‐ 2 displays a much more static flapping motion, that is, in a see‐saw‐like manner. In CDCl3, (±)‐anti‐ 1 exhibits an extraordinary upfield shift of the 1H NMR signals with increasing concentration, whereas solutions of (+)‐anti‐ 1 and the other syn/anti analogues 2 and 3 exhibit negligible or slight changes in the chemical shifts under the same conditions, which indicates that anti‐ 1 undergoes a specific heterochiral association in the solution state. Equilibrium constants for the dimerizations of (±)‐ and (+)‐anti‐ 1 in CDCl3 at 293 K were estimated by curve‐fitting analysis of the 1H NMR chemical shift dependences on concentration as 26 M ?1 [KD(racemic)] and 3.2 M ?1 [KD(homo)], respectively. The heterochiral association constant [KD(hetero)] was estimated as 98 M ?1, based on the relationship KD(racemic)=1/2 KD(homo)+1/4 KD(hetero). An inward stacking motif of interpenetrative dimer association is postulated as the mechanistic rationale for this rare case of heterochiral association. 相似文献
8.
Christian Chapuis Michel Barthe Carole Cantatore Christine Saint‐Lger Patrick Wyss 《Helvetica chimica acta》2006,89(11):2638-2653
To complete our panorama in structure–activity relationships (SARs) of sandalwood‐like alcohols derived from analogues of α‐campholenal (= (1R)‐2,2,3‐trimethylcyclopent‐3‐ene‐1‐acetaldehyde), we isomerized the epoxy‐isopropyl‐apopinene (?)‐ 2d to the corresponding unreported α‐campholenal analogue (+)‐ 4d (Scheme 1). Derived from the known 3‐demethyl‐α‐campholenal (+)‐ 4a , we prepared the saturated analogue (+)‐ 5a by hydrogenation, while the heterocyclic aldehyde (+)‐ 5b was obtained via a Bayer‐Villiger reaction from the known methyl ketone (+)‐ 6 . Oxidative hydroboration of the known α‐campholenal acetal (?)‐ 8b allowed, after subsequent oxidation of alcohol (+)‐ 9b to ketone (+)‐ 10 , and appropriate alkyl Grignard reaction, access to the 3,4‐disubstituted analogues (+)‐ 4f,g following dehydration and deprotection. (Scheme 2). Epoxidation of either (+)‐ 4b or its methyl ketone (+)‐ 4h , afforded stereoselectively the trans‐epoxy derivatives 11a,b , while the minor cis‐stereoisomer (+)‐ 12a was isolated by chromatography (trans/cis of the epoxy moiety relative to the C2 or C3 side chain). Alternatively, the corresponding trans‐epoxy alcohol or acetate 13a,b was obtained either by reduction/esterification from trans‐epoxy aldehyde (+)‐ 11a or by stereoselective epoxidation of the α‐campholenol (+)‐ 15a or of its acetate (?)‐ 15b , respectively. Their cis‐analogues were prepared starting from (+)‐ 12a . Either (+)‐ 4h or (?)‐ 11b , was submitted to a Bayer‐Villiger oxidation to afford acetate (?)‐ 16a . Since isomerizations of (?)‐ 16 lead preferentially to β‐campholene isomers, we followed a known procedure for the isomerization of (?)‐epoxyverbenone (?)‐ 2e to the norcampholenal analogue (+)‐ 19a . Reduction and subsequent protection afforded the silyl ether (?)‐ 19c , which was stereoselectively hydroborated under oxidative condition to afford the secondary alcohol (+)‐ 20c . Further oxidation and epimerization furnished the trans‐ketone (?)‐ 17a , a known intermediate of either (+)‐β‐necrodol (= (+)‐(1S,3S)‐2,2,3‐trimethyl‐4‐methylenecyclopentanemethanol; 17c ) or (+)‐(Z)‐lancifolol (= (1S,3R,4Z)‐2,2,3‐trimethyl‐4‐(4‐methylpent‐3‐enylidene)cyclopentanemethanol). Finally, hydrogenation of (+)‐ 4b gave the saturated cis‐aldehyde (+)‐ 21 , readily reduced to its corresponding alcohol (+)‐ 22a . Similarly, hydrogenation of β‐campholenol (= 2,3,3‐trimethylcyclopent‐1‐ene‐1‐ethanol) gave access via the cis‐alcohol rac‐ 23a , to the cis‐aldehyde rac‐ 24 . 相似文献
9.
Benjamin M. Gridley Dr. Graeme J. Moxey Dr. William Lewis Prof. Alexander J. Blake Dr. Deborah L. Kays 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(34):11446-11453
The synthesis and characterization of the first series of low‐coordinate bis(terphenyl) complexes of the Group 12 metals, [Zn(2,6‐Naph2C6H3)2] ( 1 ), [Cd(OEt2)(2,6‐Naph2C6H3)2] ( 2 ) and [Hg(OEt2)(2,6‐Naph2C6H3)2] ( 3 ) (Naph=1‐C10H7) are described. The naphthyl substituents of the terphenyl ligands confer considerable steric bulk, and as a result of limited flexibility introduce multiple conformations to these unusual systems. In the solid state, complex 1 features a two‐coordinate Zn centre with the ligands oriented in a syn/anti conformation, whereas the three‐coordinate distorted T‐shaped complexes 2 and 3 feature the ligands in the syn/syn configurations. The results of DFT calculations are in good agreement with the solid‐state configurations for these complexes and support the spectroscopic measurements, which indicate several conformers in solution. 相似文献
10.
Design,Synthesis, and Application of Chiral C2‐Symmetric Spiroketal‐Containing Ligands in Transition‐Metal Catalysis
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alonso J. Argüelles Siyuan Sun Brenna G. Budaitis Prof. Dr. Pavel Nagorny 《Angewandte Chemie (International ed. in English)》2018,57(19):5325-5329
We present an expedient and economical route to a new spiroketal‐based C2‐symmetric chiral scaffold, termed SPIROL. Based on this spirocyclic scaffold, several chiral ligands were generated. These ligands were successfully employed in an array of stereoselective transformations, including in iridium‐catalyzed hydroarylations (up to 95 % ee), palladium‐catalyzed allylic alkylations (up to 97 % ee), intermolecular palladium‐catalyzed Heck couplings (up to 94 % ee), and rhodium‐catalyzed dehydroalanine hydrogenation (up to 93 % ee). 相似文献
11.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(19):5423-5427
We present an expedient and economical route to a new spiroketal‐based C2‐symmetric chiral scaffold, termed SPIROL. Based on this spirocyclic scaffold, several chiral ligands were generated. These ligands were successfully employed in an array of stereoselective transformations, including in iridium‐catalyzed hydroarylations (up to 95 % ee), palladium‐catalyzed allylic alkylations (up to 97 % ee), intermolecular palladium‐catalyzed Heck couplings (up to 94 % ee), and rhodium‐catalyzed dehydroalanine hydrogenation (up to 93 % ee). 相似文献
12.
Jin‐Miao Tian Ai‐Fang Wang Ju‐Song Yang Xiao‐Jing Zhao Yong‐Qiang Tu Shu‐Yu Zhang Zhi‐Min Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11139-11143
A novel chiral 1,5‐N,N‐bidentate ligand based on a spirocyclic pyrrolidine oxazoline backbone was designed and prepared, and it coordinates CuBr in situ to form an unprecedented catalyst that enables efficient oxidative cross‐coupling of 2‐naphthols. Air serves as an external oxidant and generates a series of C1‐symmetric chiral BINOL derivatives with high enantioselectivity (up to 99 % ee) and good yield (up to 87 %). This approach is tolerant of a broader substrates scope, particularly substrates bearing various 3‐ and 3′‐substituents. A preliminary investigation using one of the obtained C1‐symmetric BINOL products was used as an organocatalyst, exhibiting better enantioselectivity than the previously reported organocatalyst, for the asymmetric α‐alkylation of amino esters. 相似文献
13.
LeoA. Paquette Zhenjiao Tian ChristopherK. Seekamp Tony Wang 《Helvetica chimica acta》2005,88(6):1185-1198
Two approaches for the conversion of d‐ glucose to (?) ‐neplanocin A ( 2 ), both based on the zirconocene‐promoted ring contraction of a vinyl‐substituted pyranoside, are herein evaluated (Scheme 1). In the first pathway (Scheme 2), the substrate possesses the α‐d‐ allo configuration (see 6 ) such that ultimate introduction of the nucleobase would require only an inversion of configuration. However, this precursor proved unresponsive to Cp2Zr (=[ZrCl2(Cp)2]), an end result believed to be a consequence of substantive nonbonded steric effects operating in a key intermediate (Scheme 5). In contrast, the C(2) epimer (see 7 ) experienced the desired metal‐promoted conversion to an enantiomerically pure polyfunctional cyclopentane (see 5 in Scheme 3). The substituents in this product are arrayed in a manner such that conversion to the target nucleoside can be conveniently achieved by a double‐inversion sequence (Scheme 4). Recourse to palladium(0)‐catalyzed allylic alkylation did not provide an alternate means of generating 2 . 相似文献
14.
Cross‐Aldol Reaction of Isatin with Acetone Catalyzed by Leucinol: A Mechanistic Investigation
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Mikhail A. Kabeshov Dr. Ondřej Kysilka Dr. Lubomír Rulíšek Dr. Yury V. Suleimanov Dr. Marco Bella Prof. Dr. Andrei V. Malkov Prof. Dr. Pavel Kočovský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):12026-12033
Comprehensive mechanistic studies on the enantioselective aldol reaction between isatin ( 1 a ) and acetone, catalyzed by L ‐leucinol ( 3 a ), unraveled that isatin, apart from being a substrate, also plays an active catalytic role. Conversion of the intermediate oxazolidine 4 into the reactive syn‐enamine 6 , catalyzed by isatin, was identified as the rate‐determining step by both the calculations (ΔG≠=26.1 kcal mol?1 for the analogous L ‐alaninol, 3 b ) and the kinetic isotope effect (kH/kD=2.7 observed for the reaction using [D6]acetone). The subsequent reaction of the syn‐enamine 6 with isatin produces (S)‐ 2 a (calculated ΔG≠=11.6 kcal mol?1). The calculations suggest that the overall stereochemistry is controlled by two key events: 1) the isatin‐catalyzed formation of the syn‐enamine 6 , which is thermodynamically favored over its anti‐rotamer 7 by 2.3 kcal mol?1; and 2) the high preference of the syn‐enamine 6 to produce (S)‐ 2 a on reaction with isatin ( 1 a ) rather than its enantiomer (ΔΔG≠=2.6 kcal mol?1). 相似文献
15.
Olena Affolter Angelika Baro Sabine Laschat Peter Fischer 《Helvetica chimica acta》2007,90(10):1987-1999
A convenient synthetic route to enantiomerically pure tropane‐diol building blocks is described. The reaction sequence started from tropenone derivatives 1 , which were dihydroxylated to give 6,7‐dihydroxytropanone derivatives 2 . After introduction of the methoxymethyl (MOM) protecting group in diol 2a , a lipase‐mediated resolution of the resulting racemic mono‐MOM ether (±)‐ 5d with vinyl acetate and vinyl trifluoroacetate gave the acetates (?)‐ 6d and (?)‐ 6f , respectively, with 96–99% ee, and MOM ether (+)‐ 5d with up to 89% ee. Deacetylation of (?)‐ 6d afforded quantitatively MOM ether (?)‐ 5d with 99% ee, the absolute configuration of which was assigned via the modified Mosher method to be (R) at C(6). Enzymatic treatment of unprotected diol 2a with vinyl trifluoroacetate or alkoxycarbonylation resulted in the formation of Cs‐symmetrical products 9 and 12 rather than the desired desymmetrized derivatives. 相似文献
16.
Zhen Liu Jiahao Chen Hou‐Xiang Lu Xiaohan Li Yang Gao John R. Coombs Matthew J. Goldfogel Keary M. Engle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):17224-17229
We report the development of palladium(0)‐catalyzed syn‐selective 1,2‐carboboration and ‐silylation reactions of alkenes containing cleavable directing groups. With B2pin2 or PhMe2Si‐Bpin as nucleophiles and aryl/alkenyl triflates as electrophiles, a broad range of mono‐, di‐, tri‐ and tetrasubstituted alkenes are compatible in these transformations. We further describe a directed dearomative 1,2‐carboboration of electron‐rich heteroarenes by employing this approach. Through use of a removable chiral directing group, we demonstrate the viability of achieving stereoinduction in Heck‐type alkene 1,2‐difunctionalization. This work introduces new avenues to access highly functionalized boronates and silanes with precise regio‐ and stereocontrol. 相似文献
17.
Zhen Liu Jiahao Chen Hou‐Xiang Lu Xiaohan Li Yang Gao John R. Coombs Matthew J. Goldfogel Keary M. Engle 《Angewandte Chemie (International ed. in English)》2019,58(47):17068-17073
We report the development of palladium(0)‐catalyzed syn‐selective 1,2‐carboboration and ‐silylation reactions of alkenes containing cleavable directing groups. With B2pin2 or PhMe2Si‐Bpin as nucleophiles and aryl/alkenyl triflates as electrophiles, a broad range of mono‐, di‐, tri‐ and tetrasubstituted alkenes are compatible in these transformations. We further describe a directed dearomative 1,2‐carboboration of electron‐rich heteroarenes by employing this approach. Through use of a removable chiral directing group, we demonstrate the viability of achieving stereoinduction in Heck‐type alkene 1,2‐difunctionalization. This work introduces new avenues to access highly functionalized boronates and silanes with precise regio‐ and stereocontrol. 相似文献
18.
Protecting‐Group‐Free Enantioselective Synthesis of (−)‐Pallavicinin and (+)‐Neopallavicinin
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bin Huang Lei Guo Prof. Yanxing Jia 《Angewandte Chemie (International ed. in English)》2015,54(46):13599-13603
The first enantioselective synthesis of (?)‐pallavicinin and (+)‐neopallavicinin has been achieved in 15 steps. The described synthesis avoids protecting‐group manipulations by synthesis designs predicated on highly chemo‐ and stereoselective transformations. Highlights of the synthesis include a palladium‐catalyzed enantioselective decarboxylative allylation to form the chiral all‐carbon quaternary stereocenter, a palladium‐catalyzed oxidative cyclization to assemble the [3.2.1]‐bicyclic moiety, and an unprecedented LiBHEt3‐induced fragmentation/protonation of an α‐hydroxy epoxide to form the α‐furan ketone with the desired configuration. 相似文献
19.
Dr. Kazuhiro Okamoto Takuya Shimbayashi Eisuke Tamura Prof. Dr. Kouichi Ohe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1490-1494
This paper describes the development of a palladium‐catalyzed decarboxylative inter‐ and intramolecular condensation reaction of isoxazol‐5(4 H)‐ones with carbonyl compounds in the presence of PPh3, giving various 2‐azabuta‐1,3‐dienes or pyrroles in moderate to high yields. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(12):3382-3386
An asymmetric synthesis of C 3‐symmetric triangular macrocycles is reported. 1‐Methylsulfonyl‐4‐(4‐vinylphenyl)‐1,2,3‐triazole undergoes a rhodium(II)‐catalyzed cyclotrimerization to establish an enantiopure C 3‐symmetric triangular macrocycle motif. This method can be applied to the synthesis of an enantiopure hydrocarbon, which owes its chirality to asymmetric distribution of H/D atoms on the benzene rings. 相似文献