- Hydration of Cyanohydrins by Highly Active Cationic Pt Catalysts: Mechanism and Scope
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Cyanohydrins (α-hydroxy nitriles) are a special type of nitriles that readily decompose into hydrogen cyanide (HCN) and the corresponding carbonyl compounds. Hydration of cyanohydrins that are readily available through cyanation of aldehydes and ketones provides the most straightforward route to valuable α-hydroxyamides. However, due to low stability of cyanohydrins and deactivation of the catalysts by the released HCN, catalytic direct hydration of cyanohydrins still remains largely unsolved. As a general trend, cyanohydrins containing bulkier substituents, such as α,α-diaryl cyanohydrins, degrade more quickly and thus are more difficult to be hydrated. Here, we report development of cationic platinum catalysts that exhibit high reactivity for hydration of various cyanohydrins. Detailed mechanistic investigations for hydration of nitriles by (PμP)Pt(PR2OH)X(OTf) reveal a catalytic cycle involving the formation of a five-membered metallacyclic intermediate and subsequent hydrolysis via attacking on the phosphorus of the secondary phosphine oxide (PR2OH) ligand by H2O. We discovered that Pt catalyst A bearing the electron-rich, appropriately small-bite-angle bisphosphine ligand provides super reactivity for hydration of cyanohydrins. The hydration reactions catalyzed by A proceed at ambient temperatures and occur with a wide variety of cyanohydrins, including the most difficult α,α-diaryl cyanohydrins, with good turnover numbers.
- Li, Chengcheng,Chang, Xiao-Yong,Huo, Luqiong,Tan, Haibo,Xing, Xiangyou,Xu, Chen
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p. 8716 - 8726
(2021/07/26)
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- Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical-Polar Crossover Cyclopropanation of Alkenes
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A general protocol for visible-light-induced cyclopropanation of alkenes was developed with bromomethyl silicate as a methylene transfer reagent, offering a robust tool for accessing highly valuable cyclopropanes. In addition to α-aryl or methyl-substituted Michael acceptors and styrene derivatives, the unactivated 1,1-dialkyl ethylenes were also shown to be viable substrates. Apart from realizing the cyclopropanation of terminal alkenes, the methyl transfer reaction has been further demonstrated to be amenable to the internal olefins. The photocatalytic cyclopropanation of 1,3-bis(1-arylethenyl)benzenes was also achieved, giving polycyclopropane derivatives in excellent yields. With late-stage cyclopropanation as the key strategy, the synthetic utility of this transformation was also demonstrated by the total synthesis of LG100268.
- Luo, Wenping,Fang, Yewen,Zhang, Li,Xu, Tianhang,Liu, Yongjun,Li, Yan,Jin, Xiaoping,Bao, Jiakan,Wu, Xiaodong,Zhang, Zongyong
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supporting information
p. 1778 - 1781
(2020/03/11)
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- Tranylcypromine-Based LSD1 Inhibitors: Structure-Activity Relationships, Antiproliferative Effects in Leukemia, and Gene Target Modulation
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Abstract: LSD1 is a lysine demethylase highly involved in initiation and development of cancer. To design highly effective covalent inhibitors, a strategy is to fill its large catalytic cleft by designing tranylcypromine (TCP) analogs decorated with long,
- Fioravanti, Rossella,Romanelli, Annalisa,Mautone, Nicola,Di Bello, Elisabetta,Rovere, Annarita,Corinti, Davide,Zwergel, Clemens,Valente, Sergio,Rotili, Dante,Botrugno, Oronza A.,Dessanti, Paola,Vultaggio, Stefania,Vianello, Paola,Cappa, Anna,Binda, Claudia,Mattevi, Andrea,Minucci, Saverio,Mercurio, Ciro,Varasi, Mario,Mai, Antonello
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p. 643 - 658
(2020/02/18)
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- Visible-Light-Promoted Redox-Neutral Cyclopropanation Reactions of α-Substituted Vinylphosphonates and Other Michael Acceptors with Chloromethyl Silicate as Methylene Transfer Reagent
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The alkene cyclopropanation with chloromethyl silicate as a methylene transfer reagent has been accomplished via visible-light-mediated redox-neutral catalysis. This method features broad functional group tolerance and mild conditions. In addition to α-substituted vinylphosphonates, a range of Michael acceptors including α,β-unsaturated acrylate, ketone, amide and sulfone are suitable substrates for this photocatalytic cyclopropanation. An application of this protocol to the cyclopropanation of estrone derivative is also presented. (Figure presented.).
- Guo, Ting,Zhang, Li,Liu, Xiaobo,Fang, Yewen,Jin, Xiaoping,Yang, Yi,Li, Yan,Chen, Bin,Ouyang, Minghui
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supporting information
p. 4459 - 4463
(2018/09/14)
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- Palladium(II)-Catalyzed highly enantioselective C-H arylation of cyclopropylmethylamines
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C-H arylation via a Pd(II)/Pd(IV) catalytic cycle has been one of the most extensively studied C-H activation reactions since the 1990s. Despite the rapid development of this reaction in the past two decades, an enantioselective version has not been reported to date. Herein, we report a Pd(II)-catalyzed highly enantioselective (up to 99.5% ee) arylation of cyclopropyl C-H bonds with aryl iodides using mono-N-protected amino acid (MPAA) ligands, providing a new route for the preparation of chiral cis-aryl-cyclopropylmethylamines. The enantiocontrol is also shown to override the diastereoselectivity of chiral substrates.
- Chan, Kelvin S. L.,Fu, Hai-Yan,Yu, Jin-Quan
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supporting information
p. 2042 - 2046
(2015/03/04)
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- THIAZOLYL COMPOUNDS USEFUL AS KINASE INHIBITORS
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The invention provides compounds of formula I [INSERT CHEMICAL STRUCTURE HERE] (I) and pharmaceutically acceptable salts thereof. The formula I thiazolyl compounds inhibit tyrosine kinase activity thereby making them useful as anticancer agents and for the treatment of Alzheimer's Disease.
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Page/Page column 28
(2010/03/31)
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- Synthesis of fused [5,5]-1,2,4-triazoles via tandem thioimidate cyclopropane rearrangement-cyclization
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The synthesis of fused [5,5]-1,2,4-triazoles via a tandem cyclopropane rearrangement-cyclization sequence is described. Optimization of the cyclization reaction was achieved thermally using iPrOH as the solvent in the presence of TEA. This method was appl
- Di Marco, Christina Ng,Kuduk, Scott D.
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p. 3377 - 3386
(2007/10/03)
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- SUBSTITUTION OF THE CARBOXYL GROUP BY BROMINE IN PHENYLCYCLOPROPANECARBOXYLIC ACIDS
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The substitution of the carboxyl group by bromine in isomeric phenylcyclopropanecarboxylic acids and their noncyclic analog 2-methyl-2-phenylpropionic acid was investigated.The direction of the reaction depends significantly on the nature of the solvent, the temperature, and the mutual arrangement of the phenyl radical and the carboxyl group.A new preparative method was developed for the synthesis of 1-phenyl-1-cyclopropanecarboxylic acid.
- Sychkova, L. D.,Shabarov, Yu. S.
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p. 1775 - 1779
(2007/10/02)
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