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Highly Enantioselective Direct Synthesis of Endocyclic Vicinal Diamines through Chiral Ru(diamine)‐Catalyzed Hydrogenation of 2,2′‐Bisquinoline Derivatives 下载免费PDF全文
Wenpeng Ma Jianwei Zhang Cong Xu Fei Chen Yan‐Mei He Prof. Dr. Qing‐Hua Fan 《Angewandte Chemie (International ed. in English)》2016,55(41):12891-12894
An asymmetric hydrogenation of 2,2′‐bisquinoline and bisquinoxaline derivatives, catalyzed by chiral cationic ruthenium diamine complexes, was developed. A broad range of chiral endocyclic vicinal diamines were obtained in high yields with excellent diastereo‐ and enantioselectivity (up to 93:7 dl/meso and >99 % ee). These chiral diamines could be easily transformed into a new class of chiral N‐heterocyclic carbenes (NHCs), which are important but difficult to access. 相似文献
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Bao‐Le Li Wei‐Yang Gao Han Li Shuo‐Qing Zhang Xiao‐Qing Han Jun Lu Ren‐Xiao Liang Xin Hong Yi‐Xia Jia 《中国化学》2019,37(1):63-70
An enantioselective desymmetric nucleophilic α‐addition of cyclohexanone to propiolamide has been developed through a 6‐exo‐dig cyclization reaction. By employing simple and readily available L‐proline sodium salt as a bifunctional catalyst, a series of chiral 6,6‐bicyclic bridged products bearing morphan scaffold have been isolated in good yields and excellent enantioselectivities. Density functional theory (DFT) calculations elucidated the origins of the enantioselectivity and regioselectivity of this transformation. A salt bridge that links the amide carbonyl group with proline carboxylate in the transition state was proven to be the driving force for the induction of excellent enantioselectivity. 相似文献
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A General Strategy for the Synthesis of Enantiomerically Pure Azetidines and Aziridines through Nickel‐Catalyzed Cross‐Coupling 下载免费PDF全文
Dr. Kim L. Jensen Dennis U. Nielsen Prof. Dr. Timothy F. Jamison 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7379-7383
In this communication, we report a straightforward synthesis of enantiomerically pure 2‐alkyl azetidines. The protocol is based on a highly regioselective nickel‐catalyzed cross‐coupling of aliphatic organozinc reagents with an aziridine that features a tethered thiophenyl group. Activation by methylation transforms the sulfide into an excellent leaving group and triggers the formation of the 2‐substituted azetidine core structure by cyclization. In addition, we have expanded this concept to the synthesis of enantiomerically pure, terminal alkyl aziridines. Coupling of a TMS‐protected aziridine alcohol, followed by acidic work‐up to remove the silyl group, provides 1,2‐amino alcohol products that are readily cyclized to aziridines. Both of these sequences display excellent functional group tolerance and deliver the desired azetidine and aziridine products in good to excellent yields. 相似文献
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The 4,5‐methano‐L‐proline was used as chiral organocatalysts in direct asymmetric aldol reactions. Under the optimal conditions, excellent enantioselectivities (up to 99% ee) were obtained with high chemical yields (up to 95%) for a series of aldehydes using only 5 mol% catalyst loading. To show the practicality of the method, the reaction was tested at a large scale. The reaction was complete in 16 h, and the aldol product was obtained in 86% yield and 93% ee. 相似文献
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Chiral Calcium–BINOL Phosphate Catalyzed Diastereo‐ and Enantioselective Synthesis of syn‐1,2‐Disubstituted 1,2‐Diamines: Scope and Mechanistic Studies 下载免费PDF全文
Dr. Claudia Lalli Audrey Dumoulin Clément Lebée Dr. Fleur Drouet Vincent Guérineau Dr. David Touboul Prof. Dr. Vincent Gandon Prof. Dr. Jieping Zhu Dr. Géraldine Masson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1704-1712
A highly enantioselective, chiral, Lewis acid calcium–bis(phosphate) complex, Ca[ 3 a ]n, which catalyzes the electrophilic amination of enamides with azodicarboxylate derivatives 2 to provide versatile chiral 1,2‐hydrazinoimines 4 is disclosed. The reaction gives an easy entry to optically active syn‐1,2‐disubstituted 1,2‐diamines 6 in high yields with excellent enantioselectivities, after a one‐pot reduction of the intermediate 1,2‐hydrazinoimines 4 . The geometry and nature of the N‐substituent of the enamide affect dramatically both the reactivity and the enantioselectivity. Although the calcium–bis(phosphate) complex was a uniquely effective catalyst, the exact nature of the active catalytic species remains unclear. NMR spectroscopy and MS analysis of the various calcium complexes Ca[ 3 ]n reveals that the catalysts exist in various oligomer forms. The present mechanistic study, which includes nonlinear effects and kinetic measurements, constitutes a first step in understanding these calcium–bis(phosphate) complex catalysts. DFT calculations were carried out to explore the mechanism and the origin of the enantioselectivity with the Ca[ 3 ]n catalysts. 相似文献
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Ami Uenishi Yuya Nakagawa Hironobu Osumi Prof. Dr. Toshiro Harada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(15):4896-4905
A highly efficient and practical method for the catalytic enantioselective arylation and heteroarylation of aldehydes with organotitanium reagents, prepared in situ by the reaction of aryl‐ and heteroaryllithium reagents with ClTi(OiPr)3, is described. Titanium complexes derived from DPP‐H8‐BINOL ( 3 d ; DPP=3,5‐diphenylphenyl) and DTBP‐H8‐BINOL ( 3 e ; DTBP=3,5‐di‐tert‐butylphenyl) exhibit excellent catalytic activity in terms of enantioselectivity and turnover efficiency for the transformation, providing diaryl‐, aryl heteroaryl‐, and diheteroarylmethanol derivatives in high enantioselectivity at low catalyst loading (0.2–2 mol %). The reaction begins with a variety of aryl and heteroaryl bromides through their conversion into organolithium intermediates by Br/Li exchange with nBuLi, thus providing straightforward access to a range of enantioenriched alcohols from commercially available starting materials. Various 2‐thienylmethanols can be synthesized enantioselectively by using commercially available 2‐thienyllithium in THF. The reaction can be carried out on a 10 mmol scale at 0.5 mol % catalyst loading, demonstrating its preparative utility. 相似文献
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Alexander M. Haydl Lukas J. Hilpert Prof. Dr. Bernhard Breit 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(19):6547-6551
The rhodium‐catalyzed asymmetric N‐selective coupling of pyrazole derivatives with internal and terminal alkynes features an utmost chemo‐, regio‐, and enantioselective access to enantiopure allylic pyrazoles, readily available for incorporation in small‐molecule pharmaceuticals. This methodology is distinguished by a broad substrate scope, resulting in a remarkable compatability with a variety of different functional groups. It furthermore exhibits an intriguing case of regio‐, position‐, and enantioselectivity in just one step, underscoring the sole synthesis of just one out of up to six possible products in a highly flexible approach to allylated pyrazoles by emanating from various internal and terminal alkynes. 相似文献
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Highly Enantioselective Intramolecular 1,3‐Dipolar Cycloaddition: A Route to Piperidino‐Pyrrolizidines 下载免费PDF全文
Dr. Srinivasa Rao Vidadala Christopher Golz Prof. Dr. Carsten Strohmann Dr. Constantin‐G. Daniliuc Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(2):651-655
Enantioselective catalytic intermolecular 1,3‐dipolar cycloadditions are powerful methods for the synthesis of heterocycles. In contrast, intramolecular enantioselective 1,3‐dipolar cycloadditions are virtually unexplored. A highly enantioselective synthesis of natural‐product‐inspired pyrrolidino‐piperidines by means of an intramolecular 1,3‐dipolar cycloaddition with azomethine ylides is now reported. The method has a wide scope and yields the desired cycloadducts with four tertiary stereogenic centers with up to 99 % ee. Combining the enantioselective catalytic intramolecular 1,3‐dipolar cycloaddition with a subsequent diastereoselective intermolecular 1,3‐dipolar cycloaddition yielded complex piperidino‐pyrrolizidines with very high stereoselectivity in a one‐pot tandem reaction. 相似文献
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Palladium‐Catalyzed Enantioselective Reductive Heck Reactions: Convenient Access to 3,3‐Disubstituted 2,3‐Dihydrobenzofuran 下载免费PDF全文
Zhan‐Ming Zhang Bing Xu Yanyan Qian Lizuo Wu Yuanqi Wu Lujia Zhou Prof. Dr. Yu Liu Prof. Dr. Junliang Zhang 《Angewandte Chemie (International ed. in English)》2018,57(32):10373-10377
The first example of highly enantioselective intramolecular hydroarylation of allyl aryl ethers was realized by palladium‐catalyzed reductive heck reactions utilizing a new chiral sulfinamide phosphine ligand (N‐Me‐ XuPhos ). N‐Me‐ XuPhos can be easily prepared on gram scale from readily available starting materials in a one‐pot synthesis approach. A series of optically active 2,3‐dihydrobenzofurans bearing a quaternary stereocenter were obtained in good yields and with excellent enantioselectivities. The practicality of this reaction was validated in the straightforward synthesis of CB2 receptor agonists. Moreover, deuterium was efficiently incorporated into the products. 相似文献
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Construction of a Chiral Silicon Center by Rhodium‐Catalyzed Enantioselective Intramolecular Hydrosilylation 下载免费PDF全文
Dr. Yuki Naganawa Tomoya Namba Mayu Kawagishi Prof. Dr. Hisao Nishiyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9319-9322
Rhodium‐catalyzed enantioselective desymmetrizing intramolecular hydrosilylation of symmetrically disubstituted hydrosilanes is described. The original axially chiral phenanthroline ligand (S)‐BinThro (Binol‐derived phenanthroline) was found to work as an effective chiral catalyst for this transformation. A chiral silicon stereogenic center is one of the chiral motifs gaining much attention in asymmetric syntheses and the present protocol provides cyclic five‐membered organosilanes incorporating chiral silicon centers with high enantioselectivities (up to 91 % ee). The putative active RhI catalyst takes the form of an N,N,O‐tridentate coordination complex, as determined by several complementary experiments. 相似文献