- Crystal-to-Crystal Synthesis of Photocatalytic Metal–Organic Frameworks for Visible-Light Reductive Coupling and Mechanistic Investigations
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Postmodification of reticular materials with well-defined catalysts is an appealing approach to produce new catalytic functional materials with improved stability and recyclability, but also to study catalysis in confined spaces. A promising strategy to this end is the postfunctionalization of crystalline and robust metal–organic frameworks (MOFs) to exploit the potential of crystal-to-crystal transformations for further characterization of the catalysts. In this regard, two new photocatalytic materials, MOF-520-PC1 and MOF-520-PC2, are straightforwardly obtained by the postfunctionalization of MOF-520 with perylene-3-carboxylic acid (PC1) and perylene-3-butyric acid (PC2). The single crystal-to-crystal transformation yielded the X-ray diffraction structure of catalytic MOF-520-PC2. The well-defined disposition of the perylenes inside the MOF served as suitable model systems to gain insights into the photophysical properties and mechanism by combining steady-state, time-resolved, and transient absorption spectroscopy. The resulting materials are active organophotoredox catalysts in the reductive dimerization of aromatic aldehydes, benzophenones, and imines under mild reaction conditions. Moreover, MOF-520-PC2 can be applied for synthesizing gram-scale quantities of products in continuous-flow conditions under steady-state light irradiation. This work provides an alternative approach for the construction of well-defined, metal-free, MOF-based catalysts.
- Bucci, Alberto,Escudero-Adán, Eduardo C.,Gutiérrez, Luis,Kandoth, Noufal,Lloret-Fillol, Julio,Mondal, Suvendu Sekhar,Shafir, Alexandr
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- B2pin2-Mediated Palladium-Catalyzed Diacetoxylation of Aryl Alkenes with O2 as Oxygen Source and Sole Oxidant
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A novel palladium-catalyzed alkene diacetoxylation with dioxygen (O2) as both the sole oxidant and oxygen source is developed, which was identified by 18O-isotope labeling studies. Control experiments suggested that bis(pinacolato)diboron (B2pin2) played a dominant intermediary role in the formation of a C-O bond. This method performed good functional group tolerance with moderate to excellent yields, which could be successfully applied to the late-stage modification of natural products. Furthermore, an atmospheric pressure of dioxygen enhances the practicability of the protocol.
- Huang, Jiuzhong,Ouyang, Lu,Li, Jianxiao,Zheng, Jia,Yan, Wuxin,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 5090 - 5093
(2018/09/12)
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- Metal-free reductive coupling of CO and CN bonds driven by visible light: Use of perylene as a simple photoredox catalyst
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Perylene, a simple polycyclic aromatic hydrocarbon, was used as a photoredox catalyst to enable the reductive coupling reaction of aromatic aldehydes, ketones, and an imine under visible-light irradiation using a white LED.
- Okamoto, Shusuke,Kojiyama, Keita,Tsujioka, Hiroki,Sudo, Atsushi
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supporting information
p. 11339 - 11342
(2016/09/23)
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- Metal-free, organocatalytic syn diacetoxylation of alkenes
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A novel method for the organocatalytic syn diacetoxylation of alkenes has been developed using aryl iodides as efficient catalysts. A broad range of substrates, including electron-rich as well as electron-deficient alkenes, are smoothly transformed by the new procedure, furnishing the desired products in good to excellent yields with high diastereoselectivity (up to >19:1 dr).
- Zhong, Wenhe,Liu, Shan,Yang, Jun,Meng, Xiangbao,Li, Zhongjun
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supporting information; experimental part
p. 3336 - 3339
(2012/08/29)
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- BF3·OEt2-promoted diastereoselective diacetoxylation of alkenes by PhI(OAc)2
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Selective syn and anti diacetoxylations of alkenes have been achieved using a PhI(OAc)2/BF3·OEt2 system in the presence and absence of water, respectively. A broad range of substrates including electron-deficient alkenes (such as α,β-unsaturated esters) could be elaborated efficiently at room temperature with this methodology, furnishing the desired products in good to excellent yields and diastereoselectivity. In particular, a multigram-scale diastereoselective diacetoxylation of methyl cinnamate (5.00 g) was also accomplished in a few hours, maintaining the same efficiency as small-scale reaction. This novel methodology provides an alternative approach for the preparation of various 1,2-diols.
- Zhong, Wenhe,Yang, Jun,Meng, Xiangbao,Li, Zhongjun
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experimental part
p. 9997 - 10004
(2012/02/05)
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- Bis(NHC)-palladium(II) complex-catalyzed dioxygenation of alkenes
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Bis(NHC)-Pd(II) complexes derived from l,l'-binaphthyl-2,2'-diamine (BINAM) were successfully first used to catalyze the dioxygenation of alkenes under mild conditions tolerant of air and moisture. Cationic NHC-Pd2+ diaquo complex 1e showed the highest catalytic activity to give 1,2dioxygenation products with good syn-diastereoselectivity for 1,2-disubstituted alkenes.
- Wang, Wenfeng,Wang, Feijun,Shi, Min
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experimental part
p. 928 - 933
(2010/05/01)
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- Efficient diacetoxylation of alkenes via Pd(II)/Pd(IV) process with peracetic acid and acetic anhydride
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A palladium-catalyzed diacetoxylation of alkenes in the presence of peracetic acid and acetic anhydride was developed to produce diacetates efficiently and diastereoselectively. Due to its mild conditions, this method was suitable for a broad range of substrates encompassing conjugated and nonconjugated olefins.
- Park, Chan Pil,Lee, Joo Ho,Yoo, Kyung Soo,Jung, Kyung Woon
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supporting information; experimental part
p. 2450 - 2452
(2010/07/05)
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- Palladium-catalyzed olefin dioxygenation
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A general method for the vicinal dioxygenation of olefins was developed using cationic Pd diphosphine complexes as the catalysts and PhI(OAc)2 as the terminal oxidant. In comparison to known Pd-catalyzed vicinal oxidations, this method is suitable for a broad range of olefins in both inter- and intramolecular reactions. An 18O-labeling experiment provides insight into the mechanism of this transformation which presumably involves Pd(II)/Pd(IV) intermediates. Copyright
- Li, Yang,Song, Datong,Dong, Vy M.
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p. 2962 - 2964
(2008/09/20)
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- Reductive esterification of aromatic aldehydes using Zn/Ac 2O/imidazole or Zn/Yb(OTf)3/(RCO)2O system
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Benzaldehydes are reduced by metallic zinc in the presence of Ac 2O and imidazole, giving the corresponding benzyl acetates in good yields. Reductive esterification of aromatic aldehydes is also carried out via gem-diacetoxy compounds. Carbonyl compounds are readily converted to the gem-diacyloxy compounds in excellent yields on treatment with 2molar amounts of acid anhydride and 10mol% of Yb(OTf)3 in MeCN at room temperature. Thus-formed diacyloxy compounds derived from aromatic aldehydes are reduced in situ by metallic zinc to afford the corresponding esters.
- Hirao, Toshikazu,Santhitikul, Sirida,Takeuchi, Hiroki,Ogawa, Akiya,Sakurai, Hidehiro
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p. 10147 - 10152
(2007/10/03)
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- Mechanistic insight into the lanthanide (III) salt catalysed monoacylation of symmetrical diols from structural models
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Model studies are presented that suggest the mechanism of the lanthanide(III) salt catalysed mono acylation of symmetrical diols proceeds via chelation of the diol and the anhydride to the lanthanide salt, followed by an 'intramolecular' acyl transfer.
- Clarke, Paul A.,Arnold, Polly L.,Smith, Martin A.,Natrajan, Louise S.,Wilson, Claire,Chan, Chuen
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p. 2588 - 2589
(2007/10/03)
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- A one-step procedure for the monoacylation of symmetrical 1,2-diols
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A series of lanthanide (III) salts have been shown to catalyze the monoacylation of symmetrical 1,2-diols by carboxylic acid anhydrides with surprisingly high selectivity.
- Clarke, Paul A.,Kayaleh, Nadim E.,Smith, Martin A.,Baker, James R.,Bird, Stephan J.,Chan, Chuen
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p. 5226 - 5231
(2007/10/03)
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- Catalytic pinacol coupling in the presence of acylating reagent
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Catalytic pinacol coupling reaction takes place in the presence of an acetylating reagent such as Ac2O or AcCl. When aromatic aldehydes are treated with 3 mol% of VOCl3, 2 molar amounts of Ac2O, and zinc powder as a co-reductant, diacetylated vic-diols are obtained with high diastereoselectivity. TiCl4 can also be utilized as a catalyst with AcCl and metallic aluminum.
- Hirao,Takeuchi,Ogawa,Sakurai
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p. 1658 - 1660
(2007/10/03)
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- Oxidation of olefins and hydrazones by anodically in situ generated manganese (III) acetate
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The oxidation of olefins and hydrazones of carbonyl compounds has been performed by using in situ anodically generated milder oxidant Mn(III) acetate at Pt electrode in acetic acid. The oxidation of acyclic olefins leads to the formation of 1,2-diacetate while in the case of cyclic olefin it results in the formation of γ-lactone ring onto double bond. Further, intermolecular carbolactonization of olefins has been achieved using more reactive carboxylic acid substrate i.e. ethyl hydrogen malonate at room temperature under the similar reaction conditions. Mn(III) acetate oxidation of hydrazones of carbonyl compounds leads to its fragmentation products.
- Dubey, Shipra,Singh, Dan,Misra
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p. 548 - 552
(2007/10/03)
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- Electron-transfer Processes: Oxidation of α- and β-Alkenylbenzenes by Peroxydisulphate in Acetic Acid
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Oxidation of α- and β-unsaturated alkylbenzenes by peroxydisulphate in acetic acid gives side-chain acetoxylation with formation of the corresponding glycol diacetates and compounds (10), respectively.The reaction is catalysed by transition-metal salts, among which cupric acetate gives the best results.Generally, electron-releasing substituents on the benzene ring increase the yield and improve the selectivity.The same substrates are oxidized in water under Ag+ catalysis to the corresponding aldehydes.The different behaviour in the two solvents is ascribed to the difference in reactivity between the primary oxidation products and the starting olefin, whereas the initial oxidation step is suggested to occur in both cases via an electron-transfer process from the olefin to the sulphate radical anion.
- Citterio, Attilio,Arnoldi, Claudio,Giordano, Claudio,Castaldi, Grasiano
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p. 891 - 896
(2007/10/02)
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- STUDIES ON THE SYNTHESIS OF HETEROCYCLIC COMPOUNDS. IX. SEPARATION OF DIASTEREOMERIC DIOL COMPOUNDS
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The separation of diastereomeric diols by transformation into the corresponding dioxastannolanes was carried out.The products are solid, stable and easily separable by fractional crystallization.By reaction of acids (or acyl halides) with the stannolanes the corresponding diols (or esters) were obtained in a high degree of purity.The structures of the compounds prepared were assigned on the basis of their analytical, physical and spectral data.
- Anchisi, Carlo,Maccioni, Antonio,Maccioni, Anna Maria,Podda, Gianni
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