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1.
Dr. Vikas Tyagi Prof. Dr. Rudi Fasan 《Angewandte Chemie (International ed. in English)》2016,55(7):2512-2516
The olefination of aldehydes constitutes a most valuable and widely adopted strategy for constructing carbon–carbon double bonds in organic chemistry. While various synthetic methods have been made available for this purpose, no biocatalysts are known to mediate this transformation. Reported herein is that engineered myoglobin variants can catalyze the olefination of aldehydes in the presence of α‐diazoesters with high catalytic efficiency (up to 4,900 turnovers) and excellent E diastereoselectivity (92–99.9 % de). This transformation could be applied to the olefination of a variety of substituted benzaldehydes and heteroaromatic aldehydes, also in combination with different alkyl α‐diazoacetate reagents. This work provides a first example of biocatalytic aldehyde olefination and extends the spectrum of synthetically valuable chemical transformations accessible using metalloprotein‐based catalysts. 相似文献
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Silver(I)‐Catalyzed N‐Trifluoroethylation of Anilines and O‐Trifluoroethylation of Amides with 2,2,2‐Trifluorodiazoethane 下载免费PDF全文
Dr. Haiqing Luo Guojiao Wu Yan Zhang Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2015,54(48):14503-14507
A straightforward N‐trifluoroethylation of anilines has been developed based on silver‐catalyzed N? H insertions with 2,2,2‐trifluorodiazoethane (CF3CHN2). Mechanistically, the reaction is proposed to involve migratory insertion of a silver carbene as the key step. In contrast, when amides are employed as the substrates under similar reaction conditions, O‐trifluoroethylation occurs to afford trifluoroethyl imidates. 相似文献
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Marie‐Luis Schirmer Sven Adomeit Anke Spannenberg Thomas Werner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2458-2465
A highly efficient catalyst system for base‐free catalytic Wittig reactions has been developed and optimized. Initially, several potential (pre)catalysts as well as different silanes as reducing agents were screened. A system based on a readily available phosphine oxide as precatalyst and trimethoxy silane as reducing agent proved to be optimal. The effect of various Brønsted acidic additives was studied. Subsequently, the reaction conditions were optimized and standard reaction conditions were determined. Under these conditions the scope of this new protocol was evaluated. Nine activated olefins and 33 aldehydes were converted into 42 highly functionalized alkenes. Notably, aromatic, aliphatic as well as heteroaromatic aldehydes could be converted, giving the desired products in isolated yields up to 99 % and with good to excellent E/Z selectivities. These results underline the remarkable efficiency of this protocol considering the complexity of the reaction mixture and the four reaction steps that proceed in parallel in one pot. 相似文献
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Copper‐Catalyzed One‐Pot Denitrogenative–Dehydrogenative–Decarboxylative Coupling of β‐Ketoacids with Trifluorodiazoethane: Facile Access to Trifluoromethylated Aldol Products 下载免费PDF全文
Dr. Heng‐Ying Xiong Zhen‐Yan Yang Zhen Chen Jun‐Liang Zeng Dr. Jing Nie Prof. Jun‐An Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8325-8329
A novel copper‐catalyzed one‐pot cross‐coupling of β‐ketoacids with in situ generated trifluorodiazoethane has been developed. This reaction provides a direct and efficient method, in which one C?C bond and one C?O bond were formed in a carbenoid center with concomitant denitrogenation–dehydrogenation–decarboxylation, to afford trifluoromethylated aldol products. In several preliminary experiments, good to high enantioselectivities were also obtained. 相似文献
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Diastereoselective Synthesis of Vicinally Bis(trifluoromethylated) Alkylboron Compounds through Successive Insertions of 2,2,2‐Trifluorodiazoethane 下载免费PDF全文
Prof. Gary A. Molander DaWeon Ryu 《Angewandte Chemie (International ed. in English)》2014,53(51):14181-14185
The usefulness of embedded CF3 substituents within organic substructures necessitates the development of diverse methods for incorporating this functional group. A recently reported route to α‐trifluoromethylated alkylboron compounds by an α‐transfer mechanism has now been extended to the synthesis of unprecedented, vicinally ditrifluoromethylated alkylboron compounds in a diastereoselective fashion. The utility of these products is highlighted by conversion of the C? B bond into other functional groups. 相似文献
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Direct asymmetric aldol addition of methyl ketones to 2,2,2-trifluoro-1-phenylethanone and its ring-substituted derivatives was achieved using L-proline as a chiral promoter. Various optically active β-trifluoromethyl-β-hydroxy ketones were obtained in almost quantitative yields with moderate enantioselectivities up to 64 % ee. 相似文献
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One‐Pot Synthesis of 3‐Acetyl‐2‐aryl‐3,4‐dihydroquinazolines from N‐[2‐(Azidomethyl)phenyl]benzamides Utilizing Intramolecular Aza‐Wittig Reaction 下载免费PDF全文
Kazuhiro Kobayashi Naoki Matsumoto Mika Nagashima Hiroki Inouchi 《Helvetica chimica acta》2015,98(2):184-189
A new and convenient method for the preparation of 3,4‐dihydroquinazolines 5 with aryl and Ac groups at C(2) and N(3), respectively, has been developed. The key sequence is the formation of aza‐phosphorane intermediates by the reaction of N‐[2‐(azidomethyl)phenyl]benzamides 1 with Ph3P, followed by intramolecular aza‐Wittig reaction and 3‐acetylation, which can be conducted in one‐pot. 相似文献
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Diversity‐Oriented Synthesis of Furo[3,2‐c]coumarins and Benzofuranyl Chromenones through Chemoselective Acylation/Wittig Reaction 下载免费PDF全文
Chun‐Kai Lin Dr. Praneeth Karanam Dr. Ganapuram Madhusudhan Reddy Dr. Yi‐Ling Tsai Prof. Dr. Wenwei Lin 《Angewandte Chemie (International ed. in English)》2018,57(6):1668-1672
A highly efficient and chemoselective one‐pot protocol for the diversity‐oriented synthesis of two types of coumarin‐based formal cross‐coupling adducts, furo[3,2‐c]coumarins and 3‐benzofuranyl chromenones, is described. Key attributes of the methodology are an initial chemoselective acylation of functionalized phosphorus zwitterions and a subsequent chemoselective intramolecular Wittig reaction that preferentially resulted in one of the two coumarin derivatives in high yield, depending on relative reactivities and the addition sequence of the acylating agents. 相似文献
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A new triarylphosphine–tertiary amine bifunctional polymeric reagent has been prepared and used effectively in a variety of one‐pot Wittig reactions. The design of this reagent resolved a deficiency of a previously reported related material, and allowed it to perform more efficiently in such reactions. Furthermore, it was readily recyclable, and was also successfully applied in cascade processes involving one‐pot Wittig reactions followed by either a conjugate reduction or a reductive aldol reaction. In these reaction cascades, the phosphine oxide groups generated in the Wittig reaction served as the catalyst for the subsequent reaction. 相似文献
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Hsin‐Yi Liao 《中国化学会会志》2011,58(5):645-652
The aza‐ and arsa‐Wittig reactions HM=PH3 + O=CHX → HM=CHX + O=PH3 (M = N, As; X = H, F, Cl, Me, OMe, NMe2, CMe3) were examined using the density functional theory calculations. All of the structures were completely optimized at the B3LYP/6‐311++G** level of theory. The main finding of this work is that the difference between singlet‐triplet splitting of O=CHX and HM=PH3 play an important role in determining the kinetic and thermodynamic stability of the aza‐ and arsa‐Wittig reactions. When HM=PH3 with more ylidic character is utilized, the reaction has a smaller activation energy and a larger exothermicity. 相似文献
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3‐Iodoindole N‐carboximidamides and N‐carboximidoates 4 were prepared regioselectively via a sequential aza‐Wittig/iodine induced cyclization, starting from easily accessible 2‐alkynylphenyl iminophosphorane, isocyanates, various nucleophiles and iodine. 相似文献
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Arif Music Clment Hoarau Nicolas Hilgert Florian Zischka Dorian Didier 《Angewandte Chemie (International ed. in English)》2019,58(4):1188-1192
Described is the in situ formation of triorganocerium reagents and their application in catalyst‐free Zweifel olefinations. These unique cerium species were generated through novel exchange reactions of organohalides with n‐Bu3Ce reagents. The adequate electronegativity of cerium allowed for compensating the disadvantages of both usually functional‐group‐sensitive organolithium species and less reactive organomagnesium reagents. Exchange reactions were performed on aryl and alkenyl bromides, enabling enantiospecific transformations of chiral boron pinacol esters. Finally, these new organocerium species were engaged in selective 1,2‐additions onto enolisable and sterically hindered ketones. 相似文献
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Michiko Sasaki Dr. Hidaka Ikemoto Masatoshi Kawahata Dr. Kentaro Yamaguchi Prof. Kei Takeda Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(18):4663-4666
Don't get trapped : The effect of conjugating electron‐withdrawing groups and α‐anion‐stabilizing heteroatom substituents on configurational stability of chiral carbanions through a double bond was examined on the basis of extent of chirality transfer in intramolecular trapping in [2,3]‐Wittig rearrangement of chiral 3‐substituted 1‐propenyloxy‐1‐phenyl‐2‐propen‐1‐yl carbanions (see scheme).
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Stereoselective Total Synthesis of Oxylipins: (6S,7E,9R,10S)‐6,9,10‐Trihydroxyoctadec‐7‐enoic Acid and (6Z,8R,9R,10S)‐8,9,10‐Trihydroxyoctadec‐6‐enoic Acid 下载免费PDF全文
Jhillu Singh Yadav Kattela Shiva Shankar Anugu Srinivas Reddy Basi V. Subba Reddy 《Helvetica chimica acta》2014,97(4):546-555
The stereoselective total syntheses of oxylipins 1b and 1c are described starting from readily accessible natural sugars via the Grubbs cross‐metathesis, Wittig olefination, and Zn‐mediated reductive elimination as key steps. 相似文献
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A. D. Averin N. V. Lukashev P. Mukhaiimana A. A. Borisenko M. A. Kazankova I. P. Beletskaya 《ChemInform》2002,33(52):174-174