- Isostructurality of quinoxaline crystal phases: The interplay of weak hydrogen bonds and halogen bonding
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Tailoring the physical properties of molecular crystals though the construction of solid solutions requires the existence of isostructural crystals. Simple substitutions of a given molecular framework can give a range of different crystal structures. A se
- Bowen, Richard D.,Fenwick, Nathan W.,Saidykhan, Amie,Seaton, Colin C.,Telford, Richard
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p. 7108 - 7117
(2021/10/26)
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- Preparation and Application of Silica Films Supported Imidazolium-Based Ionic Liquid as Efficient and Recyclable Catalysts for Benzoin Condensations
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Abstract: Two silica films -immobilized imidazolium-based ionic liquids (TMICl @silica films) were prepared, characterized and utilized as efficient catalysts for the benzoin reaction. Combined characterization results from FT-IR, elemental analysis, N2 adsorption–desorption isotherms and SEM, suggested that the imidazolium-based ionic liquids were successfully immobilized on the silica films. Moreover, the catalytic performance tests demonstrated that silica films immobilized imidazolium-based ionic liquids (ILs) exhibited excellent activity for the benzoin reactions of aromatic aldehydes. The influence of catalyst concentration, temperature and reaction duration on the catalytic activity were investigated by employing 0.7TMICl @silica film(catalyst C) as the catalyst. The results also showed that the benzoin condensations of aromatic aldehydes could give desired products with satisfactory yields under the optimized conditions. Additionally, the catalyst can be effortlessly separated by filtration and reused more than five times without significant loss of activity. Graphic Abstract: [Figure not available: see fulltext.]
- Qian, Cunwei,Yao, Changsheng,Yang, Liujun,Yang, Bo,Liu, Shuchun,Liu, Zongtang
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p. 1389 - 1396
(2019/11/21)
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- The Direct Conversion of α-Hydroxyketones to Alkynes
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Alkynes are highly important functional groups in organic chemistry, both as part of target structures and as versatile synthetic intermediates. In this study, a protocol for the direct conversion of α-hydroxyketones to alkynes is reported. In combination with the variety of synthetic methods that generate the required starting materials by forming the central C-C bond, it enables a highly versatile fragment coupling approach toward alkynes. A broad scope for this novel transformation is shown alongside mechanistic insights. Furthermore, the utility of our protocol is demonstrated through its application in concert with varied α-hydroxyketone syntheses, giving access to a broad spectrum of alkynes.
- Ghiringhelli, Francesca,Nattmann, Lukas,Bognar, Sabine,Van Gemmeren, Manuel
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p. 983 - 993
(2019/01/24)
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- NaBrO3/bmim[HSO4]: a versatile system for the selective oxidation of 1,2-diols, α-hydroxyketones, and alcohols
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Abstract: Sodium bromate with bmim[HSO4] has been found to be an excellent oxidizing agent in aqueous medium. NaBrO3:bmim[HSO4] oxidized 1,2-diols, α-hydroxyketones, and alcohols to the corresponding carbonyl compounds in excellent yields. This method offers advantages such as low cost reagents, aqueous reaction conditions, moderate temperatures and short reaction times and hence environmentally benign reaction. Moreover, the ionic liquid bmim[HSO4] could be recycled for at least three times without loss of significant activity. Graphical abstract: [Figure not available: see fulltext.]
- Khurana, Jitender M.,Lumb, Anshika,Chaudhary, Ankita
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p. 381 - 386
(2017/02/10)
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- Palladium-Catalyzed Chemo- and Enantioselective C?O Bond Cleavage of α-Acyloxy Ketones by Hydrogenolysis
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A chemoselective C?O bond cleavage of the ester alkyl side-chain of α-acyloxy ketones was realized for the first time by a highly efficient palladium-catalyzed hydrogenolysis (S/C=6000, the highest catalytic efficiency by far). Furthermore, a kinetic resolution of α-acyloxy ketones was first developed by enantioselective hydrogenolysis with good yields and up to 99 % ee.
- Chen, Jianzhong,Zhang, Zhenfeng,Liu, Delong,Zhang, Wanbin
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supporting information
p. 8444 - 8447
(2016/07/19)
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- A new protocol for one-pot synthesis of tetrasubstituted pyrroles using tungstate sulfuric acid as a reusable solid catalyst
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A variety of tetrasubstituted pyrroles were synthesized in good yields in a one-pot, three-component reaction of α-hydroxyketones, malononitrile, and ammonium acetate using tungstate sulfuric acid (TSA) under solvent-free conditions.
- Farahi, Mahnaz,Davoodi, Mahdiyeh,Tahmasebi, Mina
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p. 1582 - 1584
(2018/03/22)
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- Highly enantioselective hydrogenation of o-alkoxy tetrasubstituted enamides catalyzed by a Rh/(R, S)-josiphos catalyst
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Rh/(R,S)-JosiPhos complex-catalyzed asymmetric hydrogenation of o-alkoxy tetrasubstituted enamides has been achieved, and it furnished a set of β-amino alcohol analogues in high yields and excellent enantiomeric excesses (>99% conversion, up to 99% ee).This method provides valuable chiral building blocks in chiral pharmaceuticals and useful motifs for catalysts.
- Meng, Jingjing,Gao, Min,Lv, Hui,Zhang, Xumu
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supporting information
p. 1842 - 1845
(2015/04/27)
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- Chemoselective and repetitive intermolecular cross-acyloin condensation reactions between a variety of aromatic and aliphatic aldehydes using a robust N-heterocyclic carbene catalyst
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We found that chemoselectivity of the crossed acyloin product is controlled by the adjustment of the aromatic aldehyde/aliphatic aldehyde ratio. Moreover, we observed the persistent catalytic activity of the homogeneous NHC catalyst in a solution due to N
- Jin, Ming Yu,Kim, Sun Min,Mao, Hui,Ryu, Do Hyun,Song, Choong Eui,Yang, Jung Woon
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supporting information
p. 1547 - 1550
(2014/03/21)
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- NHC-initiated cascade, metal-free synthesis of quinoxaline derivatives under solvent-free conditions
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2,3-Diaryl quinoxaline derivatives have been efficiently synthesized by cascade, metal-free, and solvent-free reaction of aryl aldehydes with aryl 1,2-diamines initiated by N-heterocyclic carbene. Compared with reported methods, this procedure has the advantages of easy work-up, reduced energy consumption, and elimination of solvent waste, hazards, and toxicity. A group of potentially bioactive compounds has been prepared for biomedical screening.
- Gao, Lijiu,Liu, Rui,Yu, Chenxia,Yao, Changsheng,Li, Tuanjie,Xiao, Zhaoxin
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p. 2131 - 2138
(2014/05/06)
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- The catalytic versatility of low toxicity dialkyltriazolium salts: In situ modification facilitates diametrically opposed catalysis modes in one pot
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The ability of triazolium salts to serve as a precatalyst for both an acid and a powerful base/nucleophile (controlled by additives) has been exploited in a process characterised by a unique in situ catalyst modification strategy. The Royal Society of Chemistry 2013.
- Myles, Lauren,Gathergood, Nicholas,Connon, Stephen J.
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supporting information
p. 5316 - 5318
(2013/06/27)
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- N-heterocyclic carbene-catalyzed annulation of α-cyano-1,4-diketones with ynals
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In this paper, the first stereoselective annulation reaction between r-cyano-1,4-diketones and ynals, mediated by catalytic amounts of a triazolium salt precatalyst and cocatalytic amounts of a weak carboxylate base, is disclosed. The title transformation proceeds smoothly under mild reaction conditions and generates three contiguous stereogenic centers, one of which is a quaternary acetal carbon. This reaction tolerates a wide variety of electronically distinct substituents on both reaction partners and affords privileged bicyclic scaffolds in 61-90% isolated yields and with up to 20:1 diastereomeric preference.
- Romanov-Michailidis, Fedor,Besnard, Celine,Alexakis, Alexandre
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supporting information
p. 4906 - 4909,4
(2012/12/12)
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- N-heterocyclic carbene-catalyzed annulation of α-cyano-1,4-diketones with ynals
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In this paper, the first stereoselective annulation reaction between r-cyano-1,4-diketones and ynals, mediated by catalytic amounts of a triazolium salt precatalyst and cocatalytic amounts of a weak carboxylate base, is disclosed. The title transformation proceeds smoothly under mild reaction conditions and generates three contiguous stereogenic centers, one of which is a quaternary acetal carbon. This reaction tolerates a wide variety of electronically distinct substituents on both reaction partners and affords privileged bicyclic scaffolds in 61-90% isolated yields and with up to 20:1 diastereomeric preference.
- Romanov-Michailidis, Fedor,Besnard, Céline,Alexakis, Alexandre
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supporting information
p. 4906 - 4909
(2013/01/15)
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- One-pot synthesis of quinoxalines starting from aldehydes under metal-free conditions
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An efficient and convenient synthesis of quinoxalines from easily available aldehydes was performed as a one-pot procedure in good to excellent yields under metal-free conditions, via sequential benzoin condensation, aerobic formation of benzils and condensation of the latter with 1,2-diaminobenzenes.
- Hu, Zhong-Yuan,Du, Ding,Tang, Wei-Fang,Lu, Tao
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experimental part
p. 2262 - 2264
(2012/08/07)
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- One-pot synthesis of polysubstituted imidazoles from arylaldehydes in water catalyzed by nhc using microwave irradiation
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A simple, high yielding synthesis of tri (3a-i) and tetrasubstituted (4a-g) imidazols from aldehydes is described. The cornerstone of this methodology involves the condensation of NH4OAc, substituted aldehydes, and benzoin, which is synthesized in situ from aldehydes catalyzed by N-heterocyclic carbine (NHC), under microwave irradiation in water to afford trisubstituted imidazoles (3a-i). If arylamine is added in the solution, tetrasubstituted imidazoles (4a-g) can be obtained. Lepidilines B and trifenagrel are also synthesized in high yield using this procedure. All the experiment deta are in agreement with the literature.
- Wu, Lei,Jing, Xiaobi,Zhu, Hongxiang,Liu, Yinlin,Yan, Chaoguo
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p. 1204 - 1207
(2013/03/28)
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- Highly chemoselective direct crossed aliphatic-aromatic acyloin condensations with triazolium-derived carbene catalysts
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It has been shown for the first time that triazolium precatalysts promote (in the presence of base) highly chemoselective crossed acyloin condensation reactions between aliphatic and ortho-substituted aromatic aldehydes. An o-bromine atom can serve as a temporary directing group to ensure high chemoselectivity (regardless of the nature of the other substituents on the aromatic ring) which then can be conveniently removed. The process is of broad scope and is operationally simple as it does not require the preactivation of any of the coupling partners to ensure selectivtiy. Preliminary data indicate that highly enantioselective variants of the reaction are feasible using chiral precatalysts.
- O'Toole, Sarah E.,Rose, Christopher A.,Gundala, Sivaji,Zeitler, Kirsten,Connon, Stephen J.
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supporting information; experimental part
p. 347 - 357
(2011/04/17)
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- NHC triggered cascade metal-free synthesis of 2,3-diarylated indoles under solvent-free conditions
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A new cascade strategy to the synthesis of 2,3-diarylated indoles via the metal-free reaction of aryl aldehyde and aryl amine triggered by N-heterocyclic carbene (NHC) under solvent-free conditions, has been disclosed. The protocol has the advantages of easy work-up, high yields, wide application scope, and an environmentally benign procedure compared with the reported methods.
- Yao, Changsheng,Wang, Donglin,Lu, Jun,Qin, Bingbin,Zhang, Honghong,Li, Tuanjie,Yu, Chenxia
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supporting information; experimental part
p. 6162 - 6165
(2011/11/30)
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- Facile route to benzils from aldehydes via NHC-catalyzed benzoin condensation under metal-free conditions
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A simple and efficient one-pot procedure for the synthesis of α-diketones from aldehydes via benzoin condensation under the influence of a catalytic amount of azolium salt combined with DBU has been developed. Thus, aldehyde was allowed to react with the azolium salt/DBU catalytic system at room temperature, and then the reaction mixture was heated to 70 °C under air atmosphere to afford the corresponding 1,2-diketone in good yield. This would be an efficient alternative method of synthesizing α-diketones from aldehydes under metal-free conditions. Crown Copyright
- Shimakawa, Yuuki,Morikawa, Takashi,Sakaguchi, Satoshi
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supporting information; experimental part
p. 1786 - 1789
(2010/05/19)
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- Oxidation of benzoins to benzils using sodium hydride
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A highly efficient and eco-friendly oxidation of benzoins 1 to benzils 2 using sodium hydride has been developed.
- Joo, Cheonik,Kang, Sunhae,Kim, Sun Min,Han, Hogyu,Yang, Jung Woon
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experimental part
p. 6006 - 6007
(2010/11/21)
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- Preparation of several active N-chloro compounds from trichloroisocyanuric acid
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A very simple method for the preparation of several activeN-chloro compounds that have extensive applications in organic synthesis, industry, and medicine has been developed.Tetrachloroglycolurils, chloramine-T, N-chlorosaccharin, N-chlorosuccinimide, N-chlorophthalimide, N,N¢-dichlorophenobarbital,and N,N¢-dichlorobarbital were synthesized by chlorination with trichloroisocyanuric acid under mild reaction conditions at roomtemperature. This method is clean, fast, and efficient; the yields are also good to excellent. Georg Thieme Verlag Stuttgart.
- Shiri, Azam,Khoramabadi-Zad, Ahmad
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experimental part
p. 2797 - 2801
(2010/01/21)
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- One-step assembly of functionalized γ-butyrolactones from benzoins or benzaldehydes via an N-heterocyclic carbene-mediated tandem reaction
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(Chemical Equation Presented) We describe here a direct, efficient, one-step construction of γ,γ-difunctionalized γ-butyrolactones from benzoins or benzaldehydes via a tandem reaction promoted by 1,3-dimethyl imidazolin-2-ylidene, an N-heterocyclic carbene (NHC).
- Ye, Wei,Cai, Guanliang,Zhuang, Zeyang,Jia, Xueshun,Zhai, Hongbin
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p. 3769 - 3771
(2007/10/03)
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- Samarium diiodide promoted formation of 1,2-diketones and 1-acylamido-2-substituted benzimidazoles from N-acylbenzotriazoles
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N-Acylbenzotriazoles, when treated with samarium diiodide in THF, undergo self-coupling reaction to afford 1,2-diketones in good to excellent yields; while when treated with samarium diiodide in CH3CN, they undergo ring-opening reaction to afford 1-acylamido-2-alkyl (or aryl) benzimidazoles in reasonable to good yields. A plausible mechanism was suggested.
- Wang, Xiaoxia,Zhang, Yongmin
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p. 4201 - 4207
(2007/10/03)
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- Formation of 1,2-diketones by samarium diiodide promoted reaction of N-acylbenzotriazoles
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Transformation of N-acylbenzotriazoles 1 into 1,2-diketones 2 in good to excellent yields has been realized by the use of samarium diiodide at room temperature.
- Wang, Xiaoxia,Zhang, Yongmin
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p. 5431 - 5433
(2007/10/03)
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- Acyl-CoA::cholesterol O-Acyl Transferase (ACAT) Inhibitors. 1. 2-(Alkylthio)-4,5-diphenyl-1H-imidazoles as Potent Inhibitors of ACAT
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A potent, bioavailable ACAT inhibitor may have beneficial effects in the treatment of atherosclerosis by (i) reducing the absorption of dietary cholesterol, (ii) reducing the secretion of very low density lipoproteins into plasma from the liver, and (iii) preventing the transformation of arterial macrophages into foam cells.We have found that a mevalonate derivative 2, which contains a 4,5-diphenyl-1H-imidazol-2-yl moiety, inhibits rat hepatic microsomal ACAT in vitro and produces a significant hypocholesterolemic effect in the cholesterol-fed rat.Structure-activity relationships for analogues of 2 demonstrate that the 4,5-diphenyl-1H-imidazole moiety is a pharmacophore for inhibition of rat microsomal ACAT.
- Harris, Neil V.,Smith, Christopher,Asthon, Michael J.,Bridge, Andrew W.,Bush, Raymond C.,et al.
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p. 4384 - 4392
(2007/10/02)
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