- Polyfunctional lewis acids: Intriguing solid-state structure and selective detection and discrimination of nitroaromatic explosives
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Synthesis and crystal structures of three porphyrin-based polyfunctional Lewis acids 1-3 are reported. Intermolecular HgCl...HgCl (linear and μ-type) interactions in the solid state of the peripherally ArHgCl-decorated compound 3 lead to a fascinating 3D supramolecular architecture. Compound 3 shows a selective fluorescence quenching response to picric acid and discriminates other nitroaromatic-based explosives. For the first time, an electron-deficient polyfunctional Lewis acid is shown to be useful for the selective detection and discrimination of nitroaromatic explosives. The Stern-Volmer quenching constant and detection limits of compound 3 for picric acid are the best among the reported small-molecular receptors for nitroaromatic explosives. The electronic structure, Lewis acidity, and selective sensing characteristics of 3 are well corroborated by DFT calculations.
- Swamy P, Chinna Ayya,Thilagar, Pakkirisamy
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- Effect of the Molecular Conformation on Excitation Energy Transfer in Conformationally Constrained Boryl-BODIPY Dyads
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We studied the dual emission characteristics of a series of boryl-BODIPYs (1-6) comprised of triarylborane (TAB) as an energy donor and BODIPY as an energy acceptor. The molecular conformations of dyads 1-6 were systematically tuned by judiciously changing the spacer that bridged the boryl and BODIPY moieties. Frontier molecular orbitals (FMOs) are localized in 3, 4, and 6 with a twisted molecular conformation. In contrast, FMOs are significantly delocalized in 1, 2, and 5 with the least-twisted molecular conformation. Dyads 1-6 showed dual emission features when they were excited at the TAB-dominated absorption band. However, the ratio between the two emission bands in 1-6 significantly varied depending on the molecular conformations. Systematic photoluminescence (PL) studies (both steady-state and time-resolved PL) together with computational, crystal structure, and anion binding studies established that the frustrated excited-state energy transfer from borane to BODIPY is the cause of the dual emission features in these molecular dyads. These studies also revealed that the energy transfer from borane to BODIPY can be elegantly tuned by modulating the dihedral angle between these two moieties.
- Nandi, Rajendra Prasad,Chinna Ayya Swamy,Dhanalakshmi, Pandi,Behera, Santosh Kumar,Thilagar, Pakkirisamy
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Read Online
- Practical acetalization and transacetalization of carbonyl compounds catalyzed by recyclable PVP-I
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A novel PVP-I catalyzed acetalizations/transacetalizations of carbonyl compounds has been developed processing with a mild and easy handling fashion. Different types of Acyclic and cyclic acetals were prepared from carbonyl compounds or their acetals successfully. Further applications of newly developed catalytic combination were testified. This protocol featured with simplicity of operation, mild reaction condition, short reaction time, recyclable of catalyst and broad substrates scope with excellent yields.
- Cao, Fu-Rong,Lu, Guangying,Ren, Jiangmeng,Wang, Di,Zeng, Bu-Bing
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- α-Chymotrypsin-Induced Acetalization of Aldehydes and Ketones with Alcohols
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This is the first report of a simple and general method for acetalization of aldehydes via an α-chymotrypsin-induced reaction under mild conditions. A broad range of aromatic and heteroaromatic aldehydes have been acetalized under neutral conditions in good yields using a catalytic amount of chymotrypsin.
- Jiang, Guofang,Lan, Jin,Le, Zhanggao,Xie, Zongbo,Yang, Jiangnan,Zhu, Haibo
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p. 2121 - 2126
(2020/07/14)
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- Formation of Acetals and Ketals from Carbonyl Compounds: A New and Highly Efficient Method Inspired by Cationic Palladium
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The development of a new, highly efficient, and simple method for masking carbonyl groups as acetals and ketals is described. This methodology relies on the nature of the palladium catalyst to direct the acetalization/ketalization reaction. This new protocol is mild and proceed with a very low catalyst loading at ambient temperatures. The method has been extended to a wide variety of different carbonyl compounds with various steric encumbrances to form the corresponding acetals and ketals in excellent yields.
- Green, Shawn D.,Kindoll, Tyler,Lazaro-Martinez, Brenda,Mensah, Enoch A.,West, Jesse
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p. 1810 - 1814
(2019/09/09)
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- Visible-light-induced acetalization of aldehydes with alcohols
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In this work, we have achieved a simple and general method for acetalization of aldehydes by means of a photochemical reaction under low-energy visible light irradiation. A broad range of aromatic, heteroaromatic, and aliphatic aldehydes have been protected under neutral conditions in good to excellent yields using a catalytic amount of Eosin Y as the photocatalyst. Our visible light mediated acetalization strategies are successful for more challenging acid-sensitive aldehydes and sterically hindered aldehydes. Notably, this protocol is chemoselective to aldehydes, while ketones remain intact.
- Yi, Hong,Niu, Linbin,Wang, Shengchun,Liu, Tianyi,Singh, Atul K.,Lei, Aiwen
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supporting information
p. 122 - 125
(2017/11/27)
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- Triarylborane-dipyrromethane conjugates bearing dual receptor sites: The synthesis and evaluation of the anion binding site preference
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The synthesis and optical properties of four new triarylborane- dipyrromethane (TAB-DPM) conjugates (3a-d) containing dual binding sites (hydrogen bond donor and Lewis acid) have been reported. The new compounds exhibit a selective fluorogenic response towards the F- ion. The NMR titrations show that the anions bind to the TAB-DPM conjugates via the Lewis acidic triarylborane centre in preference to the hydrogen bond donor (dipyrromethane) units.
- Swamy P., Chinna Ayya,Priyanka, Ragam N.,Thilagar, Pakkirisamy
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p. 4067 - 4075
(2014/03/21)
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- Merging metal-organic framework catalysis with organocatalysis: A thiourea functionalized heterogeneous catalyst at the nanoscale
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A new thiourea-containing metal-organic framework (MOF) catalyst was synthesized. It overcomes recycling, self-aggregation and solvation issues that exist in homogeneous thiourea catalysts. Nanomorphology was introduced to increase the dispersion of the solid catalyst in solvent. Acetalization and Morita-Baylis-Hillman reactions were catalyzed using the new thiourea MOF catalyst. This journal is the Partner Organisations 2014.
- Luan, Yi,Zheng, Nannan,Qi, Yue,Tang, Jia,Wang, Ge
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p. 925 - 929
(2014/04/03)
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- Dual emissive borane-BODIPY dyads: Molecular conformation control over electronic properties and fluorescence response towards fluoride ions
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Facile synthesis of two new dimesitylboryl appended BODIPYs is reported. The two dyads have similar fluorescent chromophores but differ in their molecular conformations. They exhibit dual fluorescence, intramolecular energy transfer between boryl and BODIPY chromophores and different fluorescence responses (emission enhancement and quenching) upon fluoride binding. The Royal Society of Chemistry 2013.
- Swamy P, Chinna Ayya,Mukherjee, Sanjoy,Thilagar, Pakkirisamy
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supporting information
p. 993 - 995
(2013/02/23)
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- Bis(perfluorooctanesulfonyl)imide supported on fluorous silica gel: Application to protection of carbonyls
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The immobilization of bis(perfluorooctanesulfonyl)imide (HNPf2) on fluorous silica gel (FSG) and its utilization in protection of carbonyls have been investigated. This system is reasonably general and can be applied to converting several carbonyls to the corresponding acetals and ketals in good to excellent yields. There is no need for the use of anhydrous solvents or inert atmosphere. Recycling studies have shown that the FSG-supported HNPf2 catalyst can be readily recovered and reused several times without significant loss of activity.
- Hong, Mei,Xiao, Guomin
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experimental part
p. 121 - 126
(2012/08/28)
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- Synthesis, characterization and photochromic properties of novel naphthopyrans with hydrazone unit residue
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A series of naphthopyrans with hydrazone unit (8a-8m), were synthesized and characterized by 1H NMR, 13C NMR, IR and HRMS. The photochromic properties were investigated under continuous irradiation, in particular regard to the fatigue resistance and the lifetime of the colored open form in solution and polymers. The results showed that these compounds had both good photochromic properties and high fatigue resistance. Detailed studies showed that representative compound 8d (3,3-di-4-methoxybenzoic acid methylenehydrazino-[3H]-naphtho [2,1-b]pyran) had good photochromic properties in THF solution, in solid state, and in polymers, and exhibited a significant bathochromic shift in the spectra of the open forms compared to known naphthopyrans 9 (3,3-diphenyl-[3H]-naphtho[2,1-b]pyran). On the other hand, the higher melting points of target compounds are promising for the polymer film preparation through hot-melt method.
- Pang, Meili,Cheng, Hongbo,Niu, Yanxia,Hu, Qiaoju,Han, Jie,Meng, Jiben
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scheme or table
p. 1677 - 1684
(2012/01/12)
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- Direct conversion of acetals to esters with high regioselectivity via O,P-acetals
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A new direct conversion of O,O-acetals to esters via O,P-acetal intermediates was developed. The regioselective cleavage of unsymmetrical cyclic acetals occurred to give the more crowded esters as single isomers.
- Maegawa, Tomohiro,Otake, Kazuki,Goto, Akihiro,Fujioka, Hiromichi
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supporting information; experimental part
p. 5648 - 5651
(2011/09/15)
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- Chiral ionic liquids bearing O-silylated α,α-diphenyl (S)- Or (R)-prolinol units: Recoverable organocatalysts for asymmetric michael addition of nitroalkanes to α,β-enals
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Chiral ionic liquids bearing O-silylated α,α-diphenyl (S)- or (R)-prolinol units tagged to the imidazolium cation were synthesized and their activity as catalysts in the Michael addition of nitroalkanes to α,β-unsaturated aldehydes was evaluated. Respective (S) or (R) adducts were obtained in the reactions in high yields (up to 95 %) and with high enantio-selectivity (up to 99% ee). Remarkably, the immobilized orgariocatalysts could be used five times without any decrease in product: yields or ee values. (R)-Michael adducts could be easily transformed into the most active (R) enantiomers of medications Phenibut, Baclofen, and Rolipram for the treatment of CNS disorders.
- Maltsev, Oleg V.,Kucherenko, Alexandr S.,Beletskaya, Irina P.,Tartakovsky, Vladimir A.,Zlotin, Sergei G.
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supporting information; experimental part
p. 2927 - 2933
(2010/08/07)
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- Acid-free, organocatalytic acetalization
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The acid-free, organocatalytic acetalization of various aldehydes and ketones with N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea is presented. The neutral, double hydrogen bonding thiourea catalyst can be used at very low loadings of 0.01-1 mol% at room temperature to furnish the respective acetals in 65-99% yield at turnover frequencies around 600 h-1. Acid-labile TBDMS-protected as well as unsaturated aldehydes can be converted efficiently into their acetals utilizing this very mild and highly practical method.
- Kotke, Mike,Schreiner, Peter R.
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p. 434 - 439
(2007/10/03)
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- Cobalt(II)-catalyzed chemoselective synthesis of acetals from aldehydes
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The acetalization of aldehydes has been studied with methanol, ethanol, and 2-propanol using CoCl2 in high yields under reflux conditions. The reaction is simple, efficient, chemoselective and does not involve any other additive.
- Velusamy, Subbarayan,Punniyamurthy
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p. 4917 - 4920
(2007/10/03)
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- Zinc borates: Functionalized hard nucleophiles for coupling reactions with secondary allylic acetates
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We have succeeded in developing zinc borates of the general structure 3 for coupling reaction with allylic acetates. The advantages of using compounds 3 are their compatibility with carbonyl groups such as aldehyde, ketone, and ester groups, and their high reactivity toward secondary allylic acetates. Zinc borates 3 were prepared from boronate esters 1 [R(T) = p-(CHO)C6H4, p-(Ac)C6H4, p-{Ac(CH2)2}C6H4, p-(Ac-OCH2)C6H4, p-{AcO(CH2)3}C6H4, p-{EtO2C(CH2}2}C6H4, (E)-CH=CH(CH2)4OAc] with MeZnCl; subsequent treatment with allylic acetates 4 [R = n-C5H11, c-C6H11, (CH2)2CH(-O(CH2}2O-)] in the presence of NiCl2(PPh3)2 (10 mol-%) in THF-DMI (1,3-dimethyl-2-imidazolidinone) (10 equiv.) at 40-50 °C overnight furnished the coupling products 5 in good yields. Among the products, 5bb, possessing one free and one protected aldehyde group, is a highlight of this type of reaction. The stereochemical aspects of the reaction were also examined. Thus, the alkenyl groups of (E)- and (Z)-alkenyl borates 3b and c were transformed with retention of the olefinic geometry into acetates 4a and b (R = n-C5H11, c-C6H11), while reaction of cyclic acetate 11 proceeded with inversion at the carbon center involved in the reaction. In addition, we found that the anions generated from (EtO)2P(= O)CH2CO2Et and (MeO)2P(=O)CH2Ac under Masamune's conditions attacked the aldehyde carbon in the boronate 1d to produce - after reduction of the double bond - the boronate esters 1i and 1j, respectively, in good yields.
- Kobayashi, Yuichi,Tokoro, Yuko,Watatani, Kengo
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p. 3825 - 3834
(2007/10/03)
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- The thermally induced synthesis of N-(diethoxyphosphoryl)aldimines
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The reaction of diethyl phosphoroamidate (2) with aromatic aldehyde diethyl acetals (1) carried out at 120-160°C provides a simple, one-step preparation of N-(diethoxyphosphoryl)aldimines (3a-b). The extension of this reaction to aliphatic aldehyde diethyl acetals failed to give the expected imines.
- Zwierzak, Andrzej,Napieraj, Anna
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p. 8789 - 8794
(2007/10/03)
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- Efficient, Simple Procedures for the Large-Scale Preparation of Building Blocks for Angiotensin (II) Receptor Antagonists
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The kg-scale syntheses of p-formylbenzeneboronic acid 3c and the biphenyl derivatives 4a, 4b, and 4c, building blocks for angiotensin (II) receptor antagonists, are reported. - Keywords: Angiotensin (II) receptor antagonists/Aryl-aryl coupling/Arylboronic acid
- Jendralla, Heiner,Wagner, Adalbert,Mollath, Martina,Wunner, Joachim
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p. 1253 - 1258
(2007/10/02)
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- Contributions to the Chemistry of Boron, 206. - Preparation and Structural Characterization of p- Formylbenzeneboronic Acid
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The Grignard compound prepared from 1-bromo-4-(diethoxymethyl)benzene in tetrahydrofuran reacts with tri-n-butoxyborane to produce the title compound in 78percent yield after hydrolytic workup.The molecule crystallizes in the triclinic space group P, Z = 2, its B(OH)2 group showing extensive intermolecular hydrogen bonding.The formyl group is disordered.
- Feulner, Herta,Linti, Gerald,Noeth, Heinrich
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p. 1841 - 1843
(2007/10/02)
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- 4-(1-Azi-2,2,2-trifluoroethyl)benzoic Acid, a Highly Photolabile Carbene Generating Label Readily Fixable to Biochemical Agents
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The title compound is synthesized starting from either 4-bromobenzyl tert butyldimethylsilyl ether (5b) or 4-bromobenzyl tert-butyl ether (5c) or - most simply - from 4-bromotoluene (5a).In the first step Br was replaced by Li using n-butyllithium, then the organometallic compounds were converted into the respective trifluoroacetophenones 6a - c with N-trifluoroacetylpiperidine.The azi moiety (diazirine) was prepared from the oximes 7a - c via O-tosyloximes 8a - c plus ammonia yielding the diaziridines 9a - c and oxidation of the latter with Ag2O.Oxidation by permanganate - of the ethers after acidic cleavage - yields the title compound 12.On irradation (λ > 300 nm) 12 by elimination of N2 with a half-life period of 22 s generates the corresponding carbene.At the same time from 12 with ca. 20percent the yellow isomeric 4-(1-diazo-2,2,2-trifluoroethyl)benzoic acid (20) is formed which is photolyzed generating the same carbene as 12.The synthesis of 20 is described starting from 4-bromobenzaldehyde. - The diazirine 12 as its N-hydroxysuccinimide ester 13, or using other methods of amide synthesis, can readily be coupled to amino functions of biochemically interesting agents thus forming photoaffinity labels.
- Nassal, Michael
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p. 1510 - 1523
(2007/10/02)
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