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Oxidative Enantioselective α‐Fluorination of Aliphatic Aldehydes Enabled by N‐Heterocyclic Carbene Catalysis 下载免费PDF全文
Fangyi Li Zijun Wu Prof. Dr. Jian Wang 《Angewandte Chemie (International ed. in English)》2015,54(2):656-659
Described is the first study on oxidative enantioselective α‐fluorination of simple aliphatic aldehydes enabled by N‐heterocyclic carbene catalysis. N‐fluorobis(phenyl)sulfonimide serves as a an oxidant and as an “F” source. The C? F bond formation occurs directly at the α position of simple aliphatic aldehydes, thus overcoming nontrivial challenges, such as competitive difluorination and nonfluorination, and proceeds with high to excellent enantioselectivities. 相似文献
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Xiuqin Dong Wen Yang Weimin Hu Jianwei Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(2):670-673
The asymmetric fluorination of azolium enolates that are generated from readily available simple aliphatic aldehydes or α‐chloro aldehydes and N‐heterocyclic carbenes (NHCs) is described. The process significantly expands the synthetic utility of NHC‐catalyzed fluorination and provides facile access to a wide range of α‐fluoro esters, amides, and thioesters with excellent enantioselectivity. Pyrazole was identified as an excellent acyl transfer reagent for catalytic amide formation. 相似文献
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N‐Heterocyclic Carbene Catalyzed Cyclocondensation of α,β‐Unsaturated Carboxylic Acids: Enantioselective Synthesis of Pyrrolidinone and Dihydropyridinone Derivatives 下载免费PDF全文
Xiang‐Yu Chen Zhong‐Hua Gao Chun‐Yu Song Chun‐Lin Zhang Prof. Dr. Zhi‐Xiang Wang Prof. Dr. Song Ye 《Angewandte Chemie (International ed. in English)》2014,53(43):11611-11615
The catalytic cyclocondensation of in situ activated α,β‐unsaturated carboxylic acids was developed. N‐heterocyclic carbenes efficiently catalyzed the generation of α,β‐unsaturated acyl azolium intermediates from α,β‐unsaturated carboxylic acids via in situ generated mixed anhydrides for the enantioselective [3+2] and [3+3] cyclocondensation with α‐amino ketones and alkyl(aryl)imines, respectively. The corresponding pyrrolidinones and dihydropyridinones were isolated in good yields with high to excellent enantioselectivities. 相似文献
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N‐Heterocyclic Carbene‐Catalyzed Enantioselective Annulation of Indolin‐3‐ones with Bromoenals 下载免费PDF全文
Qijian Ni Xiaoxiao Song Prof. Dr. Gerhard Raabe Prof. Dr. Dieter Enders 《化学:亚洲杂志》2014,9(6):1535-1538
N‐Heterocyclic carbene‐catalyzed reactions of indolin‐3‐ones with 2‐bromoenals opened an asymmetric access to 3,4‐dihydropyrano[3,2‐b]indol‐2(5 H)‐ones in good yields and with good to excellent enantioselectivities. This protocol tolerates a broad substrate scope. In addition, a possible mechanism for the annulation reaction is presented. 相似文献
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Access to Spiro and Fused Indole Derivatives from α,β‐Unsaturated Aldehydes Enabled by N‐Heterocyclic Carbene Catalysis 下载免费PDF全文
Spiro and fused indoles are attractive heterocyclic compounds with broad and promising activities in various therapeutic fields, and thus, have become the synthetic targets of organic chemists. In this account, we describe our recent progress in the synthesis of a series of spiro and fused indole derivatives through N‐heterocyclic carbene (NHC)‐catalyzed annulations of diverse NHC‐bound intermediates derived from α,β‐unsaturated aldehydes. Particularly, the novel synthesized isatin‐derived α‐bromoenals may be used as versatile 1,3‐biselectrophile synthons for combination with a range of bisnucleophiles for potentially divergent syntheses of skeletally diverse spirooxindoles in the future. 相似文献
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N‐Heterocyclic Carbene Catalyzed Formal [3+2] Annulation Reaction of Enals: An Efficient Enantioselective Access to Spiro‐Heterocycles 下载免费PDF全文
Dr. Chang Guo Michael Schedler Constantin G. Daniliuc Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2014,53(38):10232-10236
A highly enantioselective N‐heterocyclic carbene (NHC) catalyzed formal [3+2] annulation of α,β‐unsaturated aldehydes with azaaurones or aurone generating spiro‐heterocycles has been developed. The protocol represents a unique NHC‐activation‐based approach to access spiro‐heterocyclic derivatives bearing a quaternary stereogenic center with high optical purity (up to 95 % ee). 相似文献
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Enantioselective Synthesis of Tertiary Propargylic Alcohols under N‐Heterocyclic Carbene Catalysis 下载免费PDF全文
Eduardo Sánchez‐Díez Dr. Maitane Fernández Dr. Uxue Uria Prof. Efraim Reyes Prof. Luisa Carrillo Prof. Jose L. Vicario 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8384-8388
A straightforward procedure to carry out the enantioselective benzoin reaction between aldehydes and ynones by employing a chiral N‐heterocyclic carbene (NHC) as catalyst was developed. Under the optimized reaction conditions, these ynones undergo a clean and selective 1,2‐addition with the catalytically generated Breslow intermediate, not observing any byproduct arising from competitive Stetter‐type reactivity. This procedure allows the preparation of tertiary alkynyl carbinols as highly enantioenriched materials, which have the remarkable potential to be used as chiral building blocks in organic synthesis. 相似文献
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Dr. Dmitry Katayev Prof. Yi‐Xia Jia Akhilesh K. Sharma Dr. Dipshikha Banerjee Dr. Céline Besnard Prof. Raghavan B. Sunoj Prof. E. Peter Kündig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):11916-11927
Palladium complexes incorporating chiral N‐heterocyclic carbene (NHC) ligands catalyze the asymmetric intramolecular α‐arylation of amides producing 3,3‐disubstituted oxindoles. Comprehensive DFT studies have been performed to gain insight into the mechanism of this transformation. Oxidative addition is shown to be rate‐determining and reductive elimination to be enantioselectivity‐determining. The synthesis of seven new NHC ligands is detailed and their performance is compared. One of them, L8 , containing a tBu and a 1‐naphthyl group at the stereogenic centre, proved superior and was very efficient in the asymmetric synthesis of fifteen new spiro‐oxindoles and three azaspiro‐oxindoles often in high yields (up to 99 %) and enantioselectivities (up to 97 % ee; ee=enantiomeric excess). Three palladacycle intermediates resulting from the oxidative addition of [Pd(NHC)] into the aryl halide bond were isolated and structurally characterized (X‐ray). Using these intermediates as catalysts showed alkene additives to play an important role in increasing turnover number and frequency. 相似文献
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NHC‐Catalyzed Asymmetric Synthesis of Functionalized Succinimides from Enals and α‐Ketoamides 下载免费PDF全文
Dr. Lei Wang Qijian Ni Marcus Blümel Tao Shu Prof. Dr. Gerhard Raabe Prof. Dr. Dieter Enders 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8033-8037
The efficient asymmetric synthesis of highly substituted succinimides from α,β‐unsaturated aldehydes and α‐ketoamides via NHC‐catalyzed [3+2] cycloaddition has been developed. The new scalable protocol significantly expands the utility of NHC catalysis for the synthesis of heterocycles and provides easy access to assemble a wide range of succinimides from simple starting materials. 相似文献
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N‐Heterocyclic Carbene Catalyzed Oxidative Coupling of Alkenes/ α‐Bromoacetophenones with Aldehydes: A Facile Entry to α,β‐Epoxy Ketones 下载免费PDF全文
Rambabu N. Reddi Pragati K. Prasad Dr. Arumugam Sudalai 《Angewandte Chemie (International ed. in English)》2015,54(47):14150-14153
A novel, N‐heterocyclic carbene (NHC) catalyzed direct oxidative coupling of styrenes with aldehydes has been described for the synthesis of α,β‐epoxy ketones in good yields. This unprecedented regioselective oxidative coupling employs NBS/DBU/DMSO (DBU=1,8‐diazabicyclo [5.4. 0] undec‐7‐ene, DMSO=dimethylsulfoxide, NBS=N‐bromosuccinimide) as an oxidative system at ambient conditions. Additionally, first NHC‐catalyzed Darzens reaction of α‐bromoketones and aldehydes under mild reaction conditions has also been described. Interestingly, mechanistic studies have revealed the preferred reactivity of NHC with alkene/α‐bromoketone rather than aldehydes, thus proceeding via the ketodeoxy Breslow intermediate. 相似文献
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Zhi‐Qin Liang Zhong‐Hua Gao Wen‐Qiang Jia Prof. Dr. Song Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1868-1872
Bifunctional N‐heterocyclic carbenes with a free hydroxy group are demonstrated as efficient catalysts for the [3+4] annulation of enals with aurones to give the corresponding benzofuran‐fused ε‐lactones in good yields with good diastereoselectivities and excellent enantioselectivities. Control experiments reveal that the [3+4] cycloadducts are kinetically favored and could be transformed to the thermodynamically favored [3+2] cycloadducts with a non‐bifunctional NHC catalyst. 相似文献