- Order from Chaos: Self-Assembly of Nanoprism from a Mixture of Tetratopic Terpyridine-Porphyrin Conformers
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Porphyrins have been widely used in the self-assembly of metallo-supramolecules. In this study, we introduced 2,2':6,2"-terpyridine (tpy) into a porphyrin core to synthesize a tetratopic building block with multiple conformers. During the self-assembly with Zn(II), such a mixture of conformers was able to form a discrete nanoprism with all building blocks in one conformation. Detailed characterizations, including NMR, ESI-MS and traveling-wave ion mobility-mass spectrometry (TWIM-MS), all supported the formation of the desired assemblies. AFM and TEM further confirmed the dimensions of assembled nanoprisms. Moreover, the photophysical properties of the ligands and complexes were noticeably different depending upon size and metal ion center.
- Filosa, Alexander,Wang, Heng,Li, Wei-Jian,Zhang, Wenjing,Ngo, Ellie,Piccolo, Jonathan E.,Yang, Hai-Bo,Li, Xiaopeng
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- Kinetic Study of the Reversible Formation of Cyclic Hemiacetals from 2-(Hydroxymethyl)benzaldehyde and 2-(β-Hydroxyethyl)benzaldehyde
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The title aldehydes 1 and 3 exist in equilibrium with cyclic hemiacetal forms 2 and 4, respectively, with equilibrium constants in water of 6.7 (12) and 20 (34).These equilibria are displaced toward the hemiacetals in strongly basic solutions because of their ionization.Acidity constants have been determined to be 12.29 (2) and 12.38 (4).The kinetics of the equilibration have been studied in the pH range 1-8 in carboxylic acid and alkylphosphonic acid buffers.The base forms (RCOO- and RPO32-) produce a common Bronsted line, while the acid forms produce two distinct Bronsted relations, with that for RHPO3- being displaced ab out one logarithmic unit above that for RCOOH.It is concluded that the former are not acting as bifunctional catalysts but owe their enhanced reactivity to an electrostatic effect.It is, moreover, suggested that the acid-catalyzed equilibrations are proceeding by way of two competing mechanisms, one involving as an intermediate the protonated hemiacetal and the other the protonated benzaldehyde.Several acetals related to 2 and 4 have also been prepared, and the kinetics and mechanism of their hydrolyses are discussed.
- Harron, John,McClelland, Robert A.,Thankachan, Chacko,Tidwell, Thomas T.
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- Dehydrogenative lactonization of diols with a platinum-loaded titanium oxide photocatalyst
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A new catalytic route for the lactonization of diols was developed by using a metal-loaded TiO2 photocatalyst. In particular, Pt-loaded rutile TiO2 exhibited a high photocatalytic activity with high selectivity. In addition, it was found that a heterogeneous acid catalyst can accelerate this photocatalytic lactonization.
- Wada, Emiko,Tyagi, Akanksha,Yamamoto, Akira,Yoshida, Hisao
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- Squaramide-catalyzed asymmetric intramolecular oxa-michael reaction of α,β-unsaturated carbonyls containing benzyl alcohol: Construction of chiral 1-substituted phthalans
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Organocatalytic enantioselective intramolecular oxa-Michael reactions of benzyl alcohol bearing α,β-unsaturated carbonyls as Michael acceptors are presented herein. Using cinchona squaramide-based organocatalyst, enones as well as α,βunsaturated esters containing benzyl alcohol provided their corresponding 1,3-dihydroisobenzofuranyl-1-methylene ketones and 1,3-dihydroisobenzofuranyl-1-methylene esters in excellent yields with high enantioselectivities. In addition, enantioenriched 1,3-dihydroisobenzofuranyl-1-methylene ketone could be obtained from the Wittig/oxa-Michael reaction cascade of 1,3-dihydro-2-benzofuran-1-ol.
- Son, Eun Chae,Kim, Seung Yeon,Kim, Sung-Gon
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p. 6826 - 6839
(2021/05/29)
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- Organocatalytic enantioselective synthesis of phthalans via Wittig/oxa-Michael cascade reaction
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An enantioselective synthetic method for 1-substituted phthalans has been developed. The organocatalytic reaction between 1,3-dihydro-2-benzofuran-1-ols and Wittig reagents using cinchona squaramide-based organocatalyst proceeded with sequential Wittig reaction followed by an enantioselective intramolecular oxa-Michael reaction, yielding enantioenriched phthalans with moderate to good enantioselectivities.
- Son, Eun Chae,No, Jaeeun,Kim, Sung-Gon
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p. 1473 - 1480
(2021/09/25)
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- IBX oxidation of benzenedimethanols in the presence of cucurbit[8]uril
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The cucurbit[8]uril (Q[8]) mediated oxidation of benzenedimethanols with o-iodoxybenzoic acid (IBX) in aqueous solution has been investigated, and the results reveal the supramolecular catalysis depends on the electronic and geometric structure of substrate. In the cases of o-benzenedimethanol (1a) and m-benzenedimethanol (1b), the IBX oxidation could be obviously enhanced by the addition of Q[8] at different extent. There is no observation of the catalytic activity of Q[8] when p-benzenedimethanol (1c) is subjected to the IBX oxidation. The addition amount of Q[8] is discussed herein, and the addition of more than 10% mol catalyst cannot improve the oxidation much more. The investigation of host-guest interactions by isothermal titration calorimetry implies the supramolecular catalysis is related to the formation of complexes between benzenedimethanols and cucurbit[8]uril. The supramolecular catalysis of Q[8] (cucurbit[8]uril) on the IBX (o-iodoxybenzoic acid) oxidation of o,m,p-benzenedimethanols in aqueous solvent and the host-guest interactions have been investigated.
- Cong, Hang,Chen, Qiuju,Geng, Qingxia,Tao, Zhu,Yamato, Takehiko
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p. 545 - 549
(2015/05/27)
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- Reaction of phthalaldehyde with aminoethanol under different conditions: Products and mechanisms of their formation
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Analysis of amino acids and very efficient disinfection procedures are based on the reaction of phthalaldehyde (OPA) with primary amines. In this contribution, aminoethanol (=kolamin) as a nitrogen-containing nucleophile was used for the investigation of its reaction mechanism with OPA performed in basic aqueous buffered media (pH 9.5), where an influence of hydration or solvation is expected, and in anhydrous acetonitrile. Depending on the detailed reaction conditions, seven products were isolated and their structures determined by NMR, mass spectrometry, and X-ray structure analysis. Reaction mechanisms are proposed, which involve hydride transfers to OPA (Cannizzaro-type reaction).
- Klima, Jiri,Polasek, Miroslav,Ludvik, Jiri,Urban, Jiri
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p. 1202 - 1209
(2013/01/15)
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- 6-membered pseudocyclic IBX acids: Syntheses, X-ray structural characterizations, and oxidation reactivities in common organic solvents
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We designed and synthesized λ5-cyclic periodinanes 1 and 2, which are homologous to IBX (1-hydroxy-1-oxo-1H-1λ5- benzo[d][1,2]iodoxol-3-one) by one carbon, to thwart close packing of molecules in the crystal lattice to permit solubility in common organic solvents and to facilitate oxidations with enhanced reactivity. The X-ray crystal structures revealed that both 1 and 2 exist in the solid state as pseudocyclic (PC) acids, i.e., 1PC and 2PC, and that the molecules in the lattice are less weakly associated as compared to those in the parent IBX due to the twisting introduced via the sp3 benzylic carbon. Both 1PC and 2PC are found to dissolve in palpable amounts in DCM and acetonitrile to allow oxidation of a variety of alcohols and sulfides to carbonyl compounds and sulfoxides in a facile manner. The subtle differences in the sterics due to methyl and ethyl substituents in 1PC and 2PC are found to manifest in contrasting reactivities in that the oxidations of alcohols occur faster with 2PC, while those of sulfides to sulfoxides occur more rapidly with 1PC.
- Moorthy, Jarugu Narasimha,Senapati, Kalyan,Parida, Keshaba Nanda
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supporting information; experimental part
p. 8416 - 8421
(2011/03/20)
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- Novel and facile selective reduction of carboxylic acid with a samarium diiodide-lanthanide triflate-methanol-base system
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The facile selective reduction of carboxylic acids in the presence of an aldehyde or that bearing a formyl group proceeded smoothly with a samarium diiodide-lanthanide triflate-methanol-base system at room temperature to give the corresponding alcohols in good to almost quantitative yield.
- Kamochi, Yasuko,Kudo, Tadahiro
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p. 341 - 344
(2007/10/03)
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- Selective Oxidations using Alumina-supported Iodobenzene Diacetate under Solvent-free Conditions
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The solid reagent system iodobenzene diacetate-alumina expeditiously and selectively oxidises Sulfides to sulfoxides and alcohols to carbonyl compounds in high yields under the influence of microwaves.
- Varma, Rajender S.,Saini, Rajesh K.,Dahiya, Rajender
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p. 120 - 121
(2007/10/03)
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- Neighboring assistance of a hydroxyl group on manganese dioxide oxidation of benzyl alcohols to lactones
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o-Hydroxymethylbenzyl alcohol and o-hydroxyethylbenzyl alcohols have been converted to phthalide and dihydroisocoumarins, very easily and in high yields, by oxidation with non-activated manganese dioxide. In contrast, the reaction of o-hydroxypropylbenzyl alcohol stopped at the aldehyde level, and afforded only a small amount of the corresponding lactone under the same condition. This implies that the first oxidation product, a benzaldehyde, could be oxidized further via a hemiacetal, but the second oxidation to lactone is very much dependent on the ability of stable intramolecular hemiacetal formation, and not on the intermolecular mode at all.
- Endo, Katsuya,Takahashi, Hiroyasu,Aihara, Minako
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p. 589 - 615
(2007/10/03)
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- Highly stereoselective cationic cyclization assisted by a sulfenyl group, scope, limitation, and mechanism
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When 8-acetoxy-2-naethyl-9-(phenylthio)-2-nonene (la) was treated with an acid, followed by a base, alkylative cyclization proceeded to give a mixture of 1,2-disubstituted cyclohexanes: 2a, 3a, and 4a. The stereochemistry of the reaction was only slightly affected by the leaving group and the reaction conditions, such as the temperature, solvent, and acid. However, the bulkiness of the sulfenyl group had a great effect on the stereochemical course of the reaction. High trans selectivity was attained when 1c (a derivative of 1a with a bulkier sulfenyl group) was used as a substrate. On the other hand, the length and rigidity of the carbon chain of the substrate also had a major effect on the stereochemistry of the reaction; a high cis selectivity was observed when 10a (a one-carbon-fewer analog of Ia) or 15a (a derivative with one more double bond in the carbon chain than in 1a) was used as the substrate. The reaction proceeded via a 6,5- or 5,5-fused-ring intermediate. The sulfenyl-group-assisted reaction could be a useful method for the stereoselective cyclization of acetates of α-sulfenylated secondary alcohols.
- Liu, Changqing,Kudo, Kazuaki,Hashimoto, Yukihiko,Saigo, Kazuhiko
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p. 494 - 502
(2007/10/02)
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- New Synthetic Strategy for the Construction of the BCD Ring System of Tanshinones
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Employing a strategy for the construction of fused furans based on an intramolecular dipolar cycloaddition reaction of nitrile oxide, the BCD ring system 3 found in the tanshinone family as a common structural unit has been synthesized.
- Shishido, Kozo,Takata, Takeshi,Omodani, Tomoki,Shibuya, Masayuki
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p. 557 - 560
(2007/10/02)
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- Carbenes and the O-H Bond: Hydroxyalkyl-Substituted Arylcarbenes
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carbene (4), phenylcarbene (19), and carbene (30) have been generated by photolysis of tosylhydrazone or diazo precursors in protic solvents.These carbenes give cyclic ethers (7, 18, 33) competitively with insertion into O-H bonds of the solvent.For comparison, the analogous benzyl cations (9, 17, 31) have been generated by solvolysis or dediazoniation.The cations are more sensitive to structural variation than their carbenic counterparts: 9 does not undergo intramolecular nucleophilic substitution, in contrast to 17 and 31.These observations are explicable in terms of high barriers for rotation about aryl-cation bonds, as compared with low barriers for rotation about aryl-carbene bonds.Two major effects of the solvent (ROH) and of the base (RONa) on product formation may be distinguished: (i) protonation of the carbene (or of its precursors) in the more acidic media leads to predominantly cationic processes; (ii) deprotonation of the OH group under strongly basic conditions enhances the nucleophilicity of the oxygen, and also facilitates insertion into the α-C-H bonds of 30.
- Kirmse, Wolfgang,Kund, Klaus
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p. 2325 - 2332
(2007/10/02)
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- CHROMIUM(VI) BASED OXIDANTS-1. CHROMIUM PEROXIDE COMPLEXES AS VERSATILE, MILD, AND EFFICIENT OXIDANTS IN ORGANIC SYNTHESIS.
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The preparation of 2,2'-bipyridylchromium peroxide, pyridinechromium peroxide, and chromium peroxide etherate is described. 2,2'-Bipyridylchromium peroxide converts different classes of alcohols to the carbonyl compounds.In 1,2-diols C-C bond cleavage occurs extensively. α-Hydroxy acids are decarboxylated quantitatively.Oximes are converted to their carbonyl compounds and thiols to their disulfides, dihydroxy phenolic compounds to quinones, benzyl amine to benzaldehyde, aromatic amines to their azo compounds, anthracene and phenanthrene to their quinones.Pyridinechromium peroxide converts different classes of alcohols efficiently to the carbonyl compounds, thiols to their disulfides, anthracene to anthraquinone.Mandelic and benzilic acids are decarboxylated very efficiently.Chromium peroxide etherate is an efficient reagent for the oxidation of different classes of alcohols to their carbonyl compounds.
- Firouzabadi, H.,Iranpoor, N.,Kiaeezadeh, F.,Toofan, J.
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p. 719 - 726
(2007/10/02)
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- DINITRATOCERIUM (IV) CHROMATE DIHYDRATE, CrO4*2H2O, A MILD REAGENT FOR THE OXIDATION OF ORGANIC COMPOUNDS IN ORGANIC MEDIA
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The title compound has been prepared and used for the oxidation of different organic substrates in benzene.
- Firouzabadi, H.,Iranpoor, N.,Kiaeezadeh, F.,Toofan, J.
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p. 973 - 982
(2007/10/02)
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- TRIS PARAPERIODATE 3 H2IO6, AN EFFICIENT AND A VERSATILE OXIDANT IN ORGANIC SYNTHESIS
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Tris paraperiodate has been prepared and used for the oxidation of different classes of organic compounds in dry benzene with high yields.
- Firouzabadi, H.,Iranpoor, N.,Hajipoor, G.,Toofan, J.
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p. 1033 - 1042
(2007/10/02)
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- BIS CHROMATE 2CrO4; A MILD OXIDANT IN ORGANIC SYNTHESIS
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Bis chromate has been prepared and used in the oxidation of benzylic alcohols to aldehydes and ketones, α-hydroxy ketones to diketones, hydroquinone to p-benzoquinone and catechol to o-benzoquinone.Cinnamyl alcohol, piperonaloxime and salycilaldoxime are rather resistant towards oxidation with this reagent.
- Firouzabadi, H.,Iranpoor, N.,Parham, H.,Tootan, J.
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p. 631 - 638
(2007/10/02)
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- BIS(2,2'-BIPYRIDYL)COPPER(II) PERMANGANATE (BBCP): A MILD AND VERSATILE OXIDANT IN ORGANIC SYNTHESIS
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The preparation of bis(2,2'-bipyridyl)copper(II) permanganate (BBCP) is described.The reagent converts alcohols to the corresponding carbonyl compounds, α-hydroxy ketones to diketones, hydroquinone to p-benzoquinone, and compounds with benzylic double bonds to benzaldehyde in high yield.Benzophenone oxime, acetophenone oxime and various benzaldoximes are converted to the corresponding carbonyl compounds, aromatic amines to azo compounds, and benzylamine to benzaldehyde, usually in high yields, under mild condition.
- Firouzabadi, H.,Sardarian, A. R.,Naderi, M.,Vessal, B.
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p. 5001 - 5004
(2007/10/02)
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