共查询到20条相似文献,搜索用时 15 毫秒
1.
Prof. Dr. Toshiaki Murai Kenta Morikawa Toshifumi Maruyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(39):13112-13119
The sequential addition of aromatic Grignard reagents to O‐alkyl thioformates proceeded to completion within 30 s to give aryl benzylic sulfanes in good yields. This reaction may begin with the nucleophilic attack of the Grignard reagent onto the carbon atom of the O‐alkyl thioformates, followed by the elimination of ROMgBr to generate aromatic thioaldehydes, which then react with a second molecule of the Grignard reagent at the sulfur atom to form arylsulfanyl benzylic Grignard reagents. To confirm the generation of aromatic thioaldehydes, the reaction between O‐alkyl thioformates and phenyl Grignard reagent was carried out in the presence of cyclopentadiene. As a result, hetero‐Diels–Alder adducts of the thioaldehyde and the diene were formed. The treatment of a mixture of the thioformate and phenyl Grignard reagent with iodine gave 1,2‐bis(phenylsulfanyl)‐1,2‐diphenyl ethane as a product, which indicated the formation of arylsulfanyl benzylic Grignard reagents in the reaction mixture. When electrophiles were added to the Grignard reagents that were generated in situ, four‐component coupling products, that is, O‐alkyl thioformates, two molecules of Grignard reagents, and electrophiles, were obtained in moderate‐to‐good yields. The use of silyl chloride or allylic bromides gave the adducts within 5 min, whereas the reaction with benzylic halides required more than 30 min. The addition to carbonyl compounds was complete within 1 min and the use of lithium bromide as an additive enhanced the yields of the four‐component coupling products. Finally, oxiranes and imines also participated in the coupling reaction. 相似文献
2.
Caitlin M. McMahon Prof. Erik J. Alexanian 《Angewandte Chemie (International ed. in English)》2014,53(23):5974-5977
A palladium‐catalyzed, intermolecular Heck‐type coupling of alkyl iodides and alkenes is described. This process is successful with a variety of primary and secondary unactivated alkyl iodides as reaction partners, including those with hydrogen atoms in the β position. The mild catalytic conditions enable intermolecular C? C bond formations with a diverse set of alkyl iodides and alkenes, including substrates containing base‐ or nucleophile‐sensitive functionality. 相似文献
3.
Pidiyara Karishma Devesh S. Agarwal Biswajit Laha Sanjay K. Mandal Rajeev Sakhuja 《化学:亚洲杂志》2019,14(23):4274-4288
A direct ortho‐Csp2‐H acylmethylation of 2‐aryl‐2,3‐dihydrophthalazine‐1,4‐diones with α‐carbonyl sulfoxonium ylides is achieved through a RuII‐catalyzed C?H bond activation process. The protocol featured high functional group tolerance on the two substrates, including aryl‐, heteroaryl‐, and alkyl‐substituted α‐carbonyl sulfoxonium ylides. Thereafter, 2‐(ortho‐acylmethylaryl)‐2,3‐dihydrophthalazine‐1,4‐diones were used as potential starting materials for the expeditious synthesis of 6‐arylphthalazino[2,3‐a]cinnoline‐8,13‐diones and 5‐acyl‐5,6‐dihydrophthalazino[2,3‐a]cinnoline‐8,13‐diones under Lawesson's reagent and BF3?OEt2 mediated conditions, respectively. Of these, the BF3?OEt2‐mediated cyclization proceeded in DMSO as a solvent and a methylene source via dual C?C and C?N bond formations. 相似文献
4.
《Angewandte Chemie (International ed. in English)》2017,56(38):11649-11652
A decarboxylative silylation of aliphatic N ‐hydroxyphthalimide (NHPI) esters using Si−B reagents as silicon pronucleophiles is reported. This C(sp3)−Si cross‐coupling is catalyzed by copper(I) and follows a radical mechanism, even with exclusion of light. Both primary and secondary alkyl groups couple effectively, whereas tertiary alkyl groups are probably too sterically hindered. The functional‐group tolerance is generally excellent, and α‐heteroatom‐substituted substrates also participate well. This enables, for example, the synthesis of α‐silylated amines starting from NHPI esters derived from α‐amino acids. The new method extends the still limited number of C(sp3)−Si cross‐couplings of unactivated alkyl electrophiles. 相似文献
5.
Heiko Lange Klaus Bergander Dr. Roland Fröhlich Dr. Seda Kehr Dr. Shuichi Nakamura Prof. Dr. Norio Shibata Prof. Dr. Takeshi Toru Prof. Dr. Dieter Hoppe Prof. Dr. 《化学:亚洲杂志》2008,3(1):88-101
Substitution reactions that employ primary‐carbamoyl‐protected arylmethanethiols are described. The enantiodetermining step was found to occur in the post‐deprotonation step as a dynamic thermodynamic resolution with a chiral bis(oxazoline) ligand. The configurationally labile lithium complexes were trapped with various electrophiles to yield different substitution products in good to excellent yields and enantiomeric excesses. The absolute configurations of the substitution products were determined, and the stereochemical pathway of the substitution reaction was elucidated for different classes of electrophiles. The temperature‐dependent epimerization process was monitored by 1H and 6Li NMR spectroscopy. 相似文献
6.
Stereoselective Synthesis and Reactions of Secondary Alkyllithium Reagents Functionalized at the 3‐Position 下载免费PDF全文
Kohei Moriya Dr. Dorian Didier Meike Simon Jeffrey M. Hammann Dr. Guillaume Berionni Prof. Dr. Konstantin Karaghiosoff Prof. Hendrik Zipse Prof. Dr. Herbert Mayr Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2015,54(9):2754-2757
Secondary alkyllithium reagents bearing an OTBS group (TBS=tert‐butyldimethylsilyl) at the 3‐position can be prepared stereoconvergently through an I/Li exchange from a diastereomeric mixture of the corresponding secondary alkyl iodides. These lithium reagents react with a range of electrophiles, including carbon electrophiles, with retention of configuration to yield various 1,3‐difunctionalized derivatives with good diastereoselectivities. Kinetic studies show that the 3‐siloxy group strongly accelerates the epimerization at the lithium‐substituted carbon atom. This method offers a new way to construct chiral open‐chain molecules with excellent stereoselectivity. 相似文献
7.
Isoxazole‐Embedded Allylic Zinc Reagent for the Diastereoselective Preparation of Highly Functionalized Aldol‐Type Derivatives Bearing a Stereocontrolled Quaternary Center 下载免费PDF全文
Lydia Klier Coura R. Diène Manuel Schickinger Albrecht Metzger Andreas J. Wagner Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Ilan Marek Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):14096-14101
Highly functionalized aldol‐type products bearing a β‐quaternary center and a stereoselectively controlled γ‐hydroxy function are readily prepared by the diastereoselective addition of an allylic zinc reagent embedded in an isoxazole ring to various aromatic and heteroaromatic aldehydes, in the presence of Lewis acids, such as MgCl2 or LaCl3?2 LiCl. After reductive cleavage of the N?O bond by using Fe, NH4Cl, aldol‐type products bearing a stereocontrolled β‐quaternary center and a γ‐hydroxy group were observed. The benzylic reactivity of the isoxazolylmethylzinc reagent towards other electrophiles, such as acid chlorides, aryl and allylic halides, as well as aldehydes in the presence of BF3?OEt2 are also described. 相似文献
8.
Diastereoselective Synthesis of Open‐Chain Secondary Alkyllithium Compounds and Trapping Reactions with Electrophiles 下载免费PDF全文
Dr. Guillaume Dagousset Kohei Moriya Rasmus Mose Dr. Guillaume Berionni Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2014,53(5):1425-1429
A practical stereoselective iodide–lithium exchange was used in the first general preparation of functionalized stereodefined acyclic secondary nonstabilized lithium reagents from the corresponding secondary alkyl iodides. These lithium reagents react with various electrophiles including carbon electrophiles with high retention of configuration. Kinetic data on the configurational stability of these acyclic alkyllithium reagents are given. This methodology offers a new entry to chiral synthons for the stereoselective synthesis of open‐chain molecules. 相似文献
9.
Carboxylic acid derivatives containing acyl halides, anhydrides, esters, amides and acyl nitriles are highly appealing electrophiles in transition‐metal‐catalyzed carbon‐carbon bond‐forming reactions due to their ready availability and low cost, which can provide divergent transformations of carboxylic acids into other value‐added products. In this Minireview, we focus on the recent advances of decarbonylative transformations of carboxylic acid derivatives in carbon‐carbon bond formations using Ni or Pd catalysts. A series of reaction types, product classifications and reaction pathways are presented herein, which show the advantageous features of carboxylic acid derivatives as alternative to aryl or alkyl halides in terms of reactivity and compatibility. The well‐accepted mechanism of nickel‐ or palladium‐catalyzed decarbonylative transformations involves initial oxidative addition of carboxylic acid derivatives, followed by decarbonylation or transmetalation (or insertion), and reductive elimination to generate the products, thereby regenerating the catalysts. 相似文献
10.
Computational Insight into Nickel‐Catalyzed Carbon–Carbon versus Carbon–Boron Coupling Reactions of Primary,Secondary, and Tertiary Alkyl Bromides 下载免费PDF全文
Dr. Man Sing Cheung Fu Kit Sheong Prof. Dr. Todd B. Marder Prof. Dr. Zhenyang Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7480-7488
The nickel‐catalyzed alkyl–alkyl cross‐coupling (C?C bond formation) and borylation (C?B bond formation) of unactivated alkyl halides reported in the literature show completely opposite reactivity orders in the reactions of primary, secondary, and tertiary alkyl bromides. The proposed NiI/NiIII catalytic cycles for these two types of bond‐formation reactions were studied computationally by means of DFT calculations at the B3LYP level. These calculations indicate that the rate‐determining step for alkyl–alkyl cross‐coupling is the reductive elimination step, whereas for borylation the rate is determined mainly by the atom‐transfer step. In borylation reactions, the boryl ligand involved has an empty p orbital, which strongly facilitates the reductive elimination step. The inability of unactivated tertiary alkyl halides to undergo alkyl–alkyl cross‐coupling is mainly due to the moderately high reductive elimination barrier. 相似文献
11.
Alexander J. Blake Lorenzo Tei Claire Wilson Martin Schrder 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(2):m43-m45
The asymmetric unit of {[4,7‐bis(2‐aminoethyl)‐1,4,7‐triazacyclononan‐1‐yl]acetato}zinc(II) triaqua{μ‐[4,7‐bis(2‐aminoethyl)‐1,4,7‐triazacyclononan‐1‐yl]acetato}lithium(I)zinc(II) chloride diperchlorate, [Zn(C12H26N5O2)][LiZn(C12H26N5O2)(H2O)3]Cl(ClO4)2, obtained from the reaction between the lithium salt of 4,7‐bis(2‐aminoethyl)‐1,4,7‐triazacyclononane‐1‐acetate and Zn(ClO4)2, contains two ZnII complexes in which each ZnII ion is six‐coordinated by five N‐atom donors and one O‐atom donor from the ligand. One carboxylate O‐atom donor is not involved in coordination to a ZnII atom, but coordinates to an Li+ ion, the tetrahedral geometry of Li+ being completed by three water molecules. The two complexes are linked via a hydrogen bond between a primary amine N—H group and the carboxylate‐O atom not involved in coordination to a metal. 相似文献
12.
Joseph Becica Oliver R. J. Heath Cameron H. M. Zheng David C. Leitch 《Angewandte Chemie (International ed. in English)》2020,59(39):17277-17281
Carboxylate esters have many desirable features as electrophiles for catalytic cross‐coupling: they are easy to access, robust during multistep synthesis, and mass‐efficient in coupling reactions. Alkenyl carboxylates, a class of readily prepared non‐aromatic electrophiles, remain difficult to functionalize through cross‐coupling. We demonstrate that Pd catalysis is effective for coupling electron‐deficient alkenyl carboxylates with arylboronic acids in the absence of base or oxidants. Furthermore, these reactions can proceed by two distinct mechanisms for C?O bond activation. A Pd0/II catalytic cycle is viable when using a Pd0 precatalyst, with turnover‐limiting C?O oxidative addition; however, an alternative pathway that involves alkene carbopalladation and β‐carboxyl elimination is proposed for PdII precatalysts. This work provides a clear path toward engaging myriad oxygen‐based electrophiles in Pd‐catalyzed cross‐coupling. 相似文献
13.
Yan‐Long Zheng Stephen G. Newman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18327-18332
While esters are frequently used as traditional electrophiles in substitution chemistry, their application in cross‐coupling chemistry is still in its infancy. This work demonstrates that methyl esters can be used as coupling electrophiles in Ni‐catalyzed Heck‐type reactions through the challenging cleavage of the C(acyl)?O bond under relatively mild reaction conditions at either 80 or 100 °C. With the σ‐NiII intermediate generated from the insertion of acyl NiII species into the tethered C=C bond, carbonyl‐retentive products were formed by domino Heck/Suzuki–Miyaura coupling and Heck/reduction pathways when organoboron and mild hydride nucleophiles are used. 相似文献
14.
Ugo Azzena Giovanna Dettori Maria Vittoria Idini Luisa Pisano Grazia Sechi 《应用有机金属化学》2003,17(11):851-855
Reductive lithiation of 3,5‐dimethoxybenzyl methyl ether was successfully performed with lithium wire and a catalytic amount of naphthalene in dry tetrahydrofuran at ?15°C, leading to the quantitative generation of 3,5‐dimethoxybenzyllithium. This organometallic compound, which can be stored for at least 24 h, was trapped with a variety of different electrophiles, including, besides aldehydes, non‐functionalized and functionalized alkyl halides and an epoxide. Accordingly, it is a useful intermediate in the synthesis of 5‐substituted natural and non‐natural resorcinols. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
15.
Asymmetric Synthesis of 1,3‐Butadienyl‐2‐carbinols by the Homoallenylboration of Aldehydes with a Chiral Phosphoric Acid Catalyst 下载免费PDF全文
Prof. Dr. Yiyong Huang Xing Yang Zongchao Lv Chen Cai Cheng Kai Prof. Dr. Yong Pei Dr. Yu Feng 《Angewandte Chemie (International ed. in English)》2015,54(25):7299-7302
Asymmetric C(sp)? C(sp2) bond formation to give enantiomerically enriched 1,3‐butadienyl‐2‐carbinols occurred through a homoallenylboration reaction between a 2,3‐dienylboronic ester and aldehydes under the catalysis of a chiral phosphoric acid (CPA). A diverse range of enantiomerically enriched butadiene‐substituted secondary alcohols with aryl, heterocyclic, and aliphatic substituents were synthesized in very high yield with high enantioselectivity. Preliminary density functional theory (DFT) calculations suggest that the reaction proceeds via a cyclic six‐membered chairlike transition state with essential hydrogen‐bond activation in the allene reagent. The catalytic reaction was amenable to the gram‐scale synthesis of a chiral alkyl butadienyl adduct, which was converted into an interesting optically pure compound bearing a benzo‐fused spirocyclic cyclopentenone framework. 相似文献
16.
Tomasz Pietrzak Iwona Justyniak Marcin Kubisiak Emil Bojarski Janusz Lewiski 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8614-8618
Over the past 150 years, a certain mythology has arisen around the mechanistic pathways of the oxygenation of organometallics with non‐redox‐active metal centers as well as the character of products formed. Notably, there is a widespread perception that the formation of commonly encountered metal alkoxide species results from the auto‐oxidation reaction, in which a parent metal alkyl compound is oxidized by the metal alkylperoxide via oxygen transfer reaction. Now, harnessing a well‐defined zinc ethylperoxide incorporating a β‐diketiminate ligand, the investigated alkylperoxide compounds do not react with the parent metal alkyl complex as well as Et2Zn to form a zinc alkoxide. Upon treatment of the zinc ethylperoxide with Et2Zn, a previously unobserved ligand exchange process is favored. Isolation of a zinc hydroxide carboxylate as a product of decomposition of the parent zinc ethylperoxide demonstrates the susceptibility of the latter to O?O bond homolysis. 相似文献
17.
Géraldine Rousseau Dr. Frédéric Robert Dr. Yannick Landais Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(42):11160-11173
The preparation and functionalization of spirocyclohexa‐2,5‐diene oxindoles is described. The spirocyclic core of the title compounds was installed by using a SmI2‐mediated cyclization of aryl iodobenzamides. Epoxidation with CF3CO3H was then carried out and was shown to occur with a high level of diastereocontrol: the reagent approaches the diene moiety syn to the amide group, which is likely to be as a consequence of hydrogen bonding between the amide C?O bond and the peracid hydrogen. Carbanionic functionalization of the spirocyclohexa‐2,5‐diene oxindoles was then examined, leading to an unprecedented rearrangement of the strained spiro system into dearomatized phenanthridinones. Upon treatment with lithium diisopropylamide (LDA) at ?40 °C, the dienes rearranged to provide a phenanthridinone lithium enolate intermediate that was trapped by electrophiles including alkyl halides and aldehydes. Interestingly, alkylation and hydroxyalkylation occurred with different regiocontrol. DFT calculations were performed that rationalize the observed skeleton rearrangement, emphasizing the role of LDA/diisopropylamine in this rearrangement. The proposed mechanism thus relies on a thermodynamically driven diisopropylamine‐mediated proton transfer with the cleavage of the diene–amide C?O bond as the key step. 相似文献
18.
Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2002,40(18):3103-3111
End‐capping reactions of a living polyester, obtained by anionic polymerization of ethylphenylketene (EPK), were carried out. As end‐capping reagents, electrophiles such as alkyl halide and acyl halide were successfully used. Reactivity of the terminal enolate and the resulting terminal structures were elucidated by model reactions, using lithium enolates having low molecular weights, obtained by an equimolar reaction of EPK with butyllithium. Polymerization of EPK by lithium alkoxide and the subsequent end‐capping reaction afforded the corresponding polyester having functional groups at both chain ends and a narrow molecular weight distribution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3103–3111, 2002 相似文献
19.
《Helvetica chimica acta》2017,100(11)
Monothiomalonates (MTM s) are surrogates of thioester enolates that allow for stereoselective C–C bond formations under mild conditions and thereby afford access to synthetically versatile thioester derivatives. Here we present a straightforward synthetic route to MTM s that proceeds through nucleophilic ring‐opening of Meldrum 's acid derivatives followed by O‐alkylation of the resulting malonic acid half thioesters with alkyl triflates or acetimidates as electrophiles. The method affords MTM s in overall yields of 34 – 92% and allows for variations of the oxo‐ and thioester moieties as well as the substituent at the C(α ) position. 相似文献
20.
Palladium‐Catalyzed Oxidative Difunctionalization of Alkenes with α‐Carbonyl Alkyl Bromides Initiated through a Heck‐type Insertion: A Route to Indolin‐2‐ones 下载免费PDF全文
Jian‐Hong Fan Wen‐Ting Wei Ming‐Bo Zhou Dr. Ren‐Jie Song Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2014,53(26):6650-6654
The oxidative interception of various σ‐alkyl palladium(II) intermediates with additional reagents for the difunctionalization of alkenes is an important research area. A new palladium‐catalyzed oxidative difunctionalization reaction of alkenes with α‐carbonyl alkyl bromides is described, in which the σ‐alkyl palladium(II) intermediate is generated through a Heck insertion and trapped using an aryl C(sp2)? H bond. This method can be applied to various α‐carbonyl alkyl bromides, including primary, secondary, and tertiary α‐bromoalkyl esters, ketones, and amides. 相似文献