- Photocatalytic Generation of π-Allyltitanium Complexes via Radical Intermediates
-
The addition of π-allylmetal complexes to carbonyls is the most important route to homoallylic alcohols. This study reports the first photocatalytic generation of π-allyltitanium complexes by a radical strategy. This novel strategy enables the three-component allylation of carbonyls with 1,3-butadiene, providing rapid access to valuable homoallylic alcohols (over 60 examples). The exceptional regio- and diastereoselectivity provided by dual photoredox/Ti catalysis is comparable to that of the Cr-catalyzed Nozaki–Hiyama–Kishi allylation reaction.
- Li, Fusheng,Lin, Shuangjie,Chen, Yuqing,Shi, Caizhe,Yan, Huaipu,Li, Chenchen,Wu, Chao,Lin, Luqing,Duan, Chunying,Shi, Lei
-
-
Read Online
- CBZ6 as a Recyclable Organic Photoreductant for Pinacol Coupling
-
A recyclable organic photoreductant (1 mol % CBZ6)-catalyzed reductive (pinacol) coupling of aldehydes, ketones, and imines has been developed. Irradiated by purple light (407 nm) using triethylamine as an electron donor, a variety of 1,2-diols and 1,2-diamines could be prepared. The oxidation potential of the excited state of CBZ6 is established as -1.92 V (vs saturated calomel electrode (SCE)). The relative high reductive potential enables the reductive coupling of carbonyl compounds and their derivatives. CBZ6 can be prepared in gram scale and is acid/base- or air-stable. It could be applied in large-scale photoreductive synthesis and recovered in high yield after the reaction.
- Wang, Hua,Qu, Jian-Ping,Kang, Yan-Biao
-
supporting information
p. 2900 - 2903
(2021/05/05)
-
- Facile pinacol coupling of aliphatic ketones by Brook rearrangement in the presence of samarium species
-
Herein we report a practical pinacol coupling reaction, in which ketones (aldehydes) react smoothly with Sm and TMSBr to afford the diol products with Sm(II) or (III) siliyl species generated in situ. This reported method affords poor yields for aromatic ketone substrates and good yields for aliphatic ketones. Therefore, it distinguishes from most reductive coupling approaches that are more effective for aromatic carbonyl compounds and provides a facile and robust approach for the pinacol coupling of aliphatic ketones. Mechanistic studies also indicated the pinacolization probably proceeded via an anionic instead of radical coupling pathway involving the Brook rearrangement in the presence of samarium (II or III) silyl species.
- Wang, Xincan,Xie, Guanqun,Zhao, Yanfei,Zheng, Ke,Fang, Yanxiong,Wang, Xiaoxia
-
supporting information
(2021/04/27)
-
- Oxidative carbon-carbon bond cleavage of 1,2-diols to carboxylic acids/ketones by an inorganic-ligand supported iron catalyst
-
The carbon-carbon bond cleavage of 1,2-diols is an important chemical transformation. Although traditional stoichiometric and catalytic oxidation methods have been widely used for this transformation, an efficient and valuable method should be further explored from the views of reusable catalysts, less waste, and convenient procedures. Herein an inorganic-ligand supported iron catalyst (NH4)3[FeMo6O18(OH)6]·7H2O was described as a heterogeneous molecular catalyst in acetic acid for this transformation in which hydrogen peroxide was used as the terminal oxidant. Under the optimized reaction conditions, carbon-carbon bond cleavage of 1,2-diols could be achieved in almost all cases and carboxylic acids or ketones could be afforded with a high conversion rate and high selectivity. Furthermore, the catalytic system was used efficiently to degrade renewable biomass oleic acid. Mechanistic insights based on the observation of the possible intermediates and control experiments are presented.
- Chen, Weiming,Xie, Xin,Zhang, Jian,Qu, Jian,Luo, Can,Lai, Yaozhu,Jiang, Feng,Yu, Han,Wei, Yongge
-
supporting information
p. 9140 - 9146
(2021/11/23)
-
- A substrate-binding metal-organic layer selectively catalyzes photoredox ene-carbonyl reductive coupling reactions
-
Intermolecular photoredox ene-carbonyl reductive coupling reactions typically have low product selectivity owing to competing dimerization and/or reduction of ketyl radicals. Herein, we report a metal-organic layer (MOL), Hf-Ir-OTf, as a bifunctional photocatalyst for selective photoredox reductive coupling of ketones or aldehydes with electron-deficient alkenes. Composed of iridium-based photosensitizers (Ir-PSs) and triflated Hf12 clusters, Hf-Ir-OTf uses Lewis acidic Hf sites to bind and activate electron-deficient alkenes to accept ketyl radicals generated by adjacent Ir-PSs, thereby suppressing undesired dimerization and reduction of ketyl radicals to enhance the selectivity for the cross-coupling products. The MOL-catalyzed reductive coupling reaction accommodates a variety of olefinic substrates and tolerates reducible groups, nicely complementing current methods for cross-coupling reactions.
- Fan, Yingjie,You, Eric,Xu, Ziwan,Lin, Wenbin
-
supporting information
p. 18871 - 18876
(2021/11/22)
-
- Crystal-to-Crystal Synthesis of Photocatalytic Metal–Organic Frameworks for Visible-Light Reductive Coupling and Mechanistic Investigations
-
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
-
-
- Photocatalytic pinacol C-C coupling and jet fuel precursor production on ZnIn2S4nanosheets
-
Visible light-driven C-C bond formation has attracted increasing attention recently, thanks to the advance in molecular photosensitizers and organometallic catalysts. Nevertheless, these homogeneous methodologies typically necessitate the utilization of noble metal-based (e.g., Ir, Ru, etc.) photosensitizers. In contrast, solid-state semiconductors represent an attractive alternative but remain less explored for C-C bond-forming reactions driven by visible-light irradiation. Herein, we report that photocatalytic pinacol C-C coupling of benzaldehyde to hydrobenzoin can be achieved on two-dimensional ZnIn2S4 nanosheets upon visible-light irradiation in the presence of a sacrificial electron donor (e.g., triethylamine). We further demonstrate that it is feasible to take advantage of both excited electrons and holes in irradiated ZnIn2S4 for C-C coupling reactions in the absence of any sacrificial reagent if benzyl alcohol is utilized as the starting substrate, maximizing the energy efficiency of photocatalysis and circumventing any byproducts. In this case, industrially important benzoin and deoxybenzoin are formed as the final products. More importantly, by judiciously tuning the photocatalytic conditions, we are able to produce either benzoin or deoxybenzoin with unprecedented high selectivity. The critical species during the photocatalytic process were systematically investigated with various scavengers. Finally, such a heterogeneous photocatalytic pinacol C-C coupling strategy was applied to produce a jet fuel precursor (e.g., hydrofuroin) from biomass-derived furanics (e.g., furfural and furfural alcohol), highlighting the promise of our approach in practical applications.
- Cao, Zhi,Han, Guanqun,Liu, Xingwu,Sun, Yujie
-
p. 9346 - 9355
(2020/10/09)
-
- Ring Closing Metathesis Approach for the Synthesis of o-Terphenyl Derivatives
-
A linear synthesis of o-terphenyl derivatives has been delineated using ring closing metathesis (RCM) as the key step. In this approach, benzil derivatives upon allyl Grignard addition provides diphenyl-1,2-diallyl dihydroxy derivatives which undergo ring closing metathesis to afford tetrahydro terphenyl derivatives. Aromatization-driven dehydration then leads to a diverse set of electron rich and electron deficient o-terphenyls. Furthermore, oxidative coupling of electron rich o-terphenyls provides the corresponding triphenylene derivatives.
- Karmakar, Shilpi,Mandal, Tirtha,Dash, Jyotirmayee
-
p. 5916 - 5924
(2019/08/21)
-
- Application of coumarin dyes for organic photoredox catalysis
-
Here we report the application of readily prepared and available coumarin dyes for photoredox catalysis, which are able to mimic powerful reductant [Ir(iii)] complexes. Coumarin derivatives 9 and 10 were employed as photoreductants in pinacol coupling and in other reactions, in the presence of Et3N as a sacrificial reducing agent. As the electronic, photophysical, and steric properties of coumarins could be varied, a wide applicability to several classes of photoredox reactions is predicted.
- Gualandi, Andrea,Rodeghiero, Giacomo,Della Rocca, Emanuele,Bertoni, Francesco,Marchini, Marianna,Perciaccante, Rossana,Jansen, Thomas Paul,Ceroni, Paola,Cozzi, Pier Giorgio
-
supporting information
p. 10044 - 10047
(2018/09/13)
-
- Organic photoredox catalyst with substrate-capture ability: A perylene derivative bearing urethane moiety for reductive coupling of ketones and aldehydes under visible light
-
A perylene derivative bearing a urethane moiety served as an efficient photoredox catalyst for the reductive coupling of ketones and aldehydes under visible light, implicating that the urethane moiety captured substrates through hydrogen bonds to lower the LUMO levels of the captured substrates, thus promoting single electron transfer from the reductant anion radical of the perylene moiety to the substrates.
- Okamoto, Shusuke,Tsujioka, Hiroki,Sudo, Atsushi
-
supporting information
p. 369 - 372
(2018/03/05)
-
- Chemoselective Photoredox Synthesis of Unprotected Primary Amines Using Ammonia
-
Unprotected α-amino carbon radicals are produced as novel intermediates via a transformation that merges acid-promoted N-H imine generation and chemoselective photocatalytic single-electron reduction. Coupling ammonia and aldehydes/ketones allows the generation of primary amines under mild conditions without the need for protecting groups. The key intermediate can be efficiently transformed into primary (di)amines by a formal dimerization, reductive amination via hydrogen atom transfer, and arylation through radical-radical coupling.
- Rong, Jiawei,Seeberger, Peter H.,Gilmore, Kerry
-
supporting information
p. 4081 - 4085
(2018/07/15)
-
- MeOH or H2O as efficient additive to switch the reactivity of allylSmBr towards carbonyl compounds
-
A variety of carbonyl compounds were treated by allylSmBr (allylSmBr) with MeOH as the cosolvent to have further insights on the previously reported reductive coupling of aryl ketones mediated by Sm/alkyl halide/MeOH. The results demonstrate that the real reducing species in Sm/alkyl halide/MeOH system should be allylSmBr, and MeOH has elegantly switched the reactivity of allylSmBr from being nucleophilic to being good reductive coupling reagent. Besides, H2O was also found to be a useful additive to realize the pinacol coupling of aliphatic aldehydes and ketones promoted by allylSmBr.
- Li, Jianyong,Niu, Qingsheng,Li, Shanchan,Sun, Yuehao,Zhou, Qian,Lv, Xin,Wang, Xiaoxia
-
supporting information
p. 1250 - 1253
(2017/03/10)
-
- Biginelli reaction of vicinal diols: A new route for one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives
-
Background: 3,4-Dihydropyrimidin-2(1H)-one derivatives are an important class of nitrogen heterocycles. These compounds present a wide range of biological activities viz antibacterial, antifungal, and antidiabetic. Although many synthetic methods are available in the literature for the synthesis of these molecules, many of these methods have their own limitations such as use of excess of expensive catalyst and poor yields. Methods: The synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives is developed through the reaction of 1,2-diols, ethyl acetoacetate and urea in the presence of lead tetraacetate in dry ethanol under reflux conditions. Results: A series of 3,4-dihydropyrimidin-2(1H)-one derivatives were synthesized in good yields (82-95%) under reflux for 2-3.5 hours in ethanol solvent. The structural assignments of these compounds were made on the basis of elemental analysis and spectroscopic data. Conclusion: This protocol is an alternative to existing procedure for the synthesis of Biginelli compounds. The present methodology reduces the number of steps in total synthesis.
- Jagadishbabu, Narasashetty,Shivashankar, Kalegowda
-
p. 330 - 336
(2017/07/26)
-
- Metal-free reductive coupling of CO and CN bonds driven by visible light: Use of perylene as a simple photoredox catalyst
-
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
-
supporting information
p. 11339 - 11342
(2016/09/23)
-
- Photoredox-Catalyzed Reductive Coupling of Aldehydes, Ketones, and Imines with Visible Light
-
Ketyl radical and amino radical anions, valuable reactive intermediates for C-C bond-forming reactions, are accessible through a C=O/C=NR umpolung. However, their utilization in catalysis remains largely underdeveloped owing to the high reduction potential of carbonyl compounds and imines. In the context of photoredox catalysis, tertiary amines are commonly employed as sacrificial co-reducing agents. Herein, an additional role of the amine is proposed, in which it is essential for the organocatalytic substrate activation. The combination of photoredox catalysis and carbonyl/imine activation enables the reductive coupling of aldehydes, ketones, and imines under mild reaction conditions.
- Nakajima, Masaki,Fava, Eleonora,Loescher, Sebastian,Jiang, Zhen,Rueping, Magnus
-
supporting information
p. 8828 - 8832
(2015/11/27)
-
- Selective Pinacol Coupling on Regeneratable Supported Acids in Sole Water
-
Efficient pinacol coupling was developed in sole water, using a reusable heterogeneous supported acid source and zinc as cheap available metal source. This medium can be easily regenerated up to 10-fold without loss of activity. Moreover, supported acids enhance the selectivity of the pinacol coupling reaction compared with homogeneous acids.
- Sotto, Nicolas,Billamboz, Muriel,Chevrin-Villette, Carole,Len, Christophe
-
p. 6375 - 6380
(2015/06/30)
-
- The scalable pinacol coupling reaction utilizing the inorganic electride [Ca2N]+·e- as an electron donor
-
The scalable pinacol coupling reaction is realized utilizing the inorganic electride [Ca2N]+·e- as an electron donor in organic solvents. The bond cleavages of the [Ca2N] + layers by methanol play a vital role in transferring anionic electrons to electrophilic aldehydes, accompanying the formation of Ca(OMe) 2 and ammonia. The Royal Society of Chemistry 2014.
- Kim, Ye Ji,Kim, Sun Min,Hosono, Hideo,Yang, Jung Woon,Kim, Sung Wng
-
supporting information
p. 4791 - 4794
(2014/05/06)
-
- Transition-metal-free and chemoselective NaOtBu-O 2-mediated oxidative cleavage reactions of vic-1,2-diols to carboxylic acids and mechanistic insight into the reaction pathways
-
A method for efficient oxidative cleavage of vic-1,2-diols using a NaO tBu-O2 system resulted in the formation of carboxylic acids in high yields. The present protocol is an eco-friendly alternative to a conventional transition-metal-based method. This new strategy allows large-scale production with nonchromatographic purification while also suppressing competitive reaction pathway such as benzilic acid rearrangement.
- Kim, Sun Min,Kim, Dong Wan,Yang, Jung Woon
-
supporting information
p. 2876 - 2879
(2014/06/23)
-
- Synthesis of ferrocene derivatives with planar chirality via palladium-catalyzed enantioselective C-H bond activation
-
The first catalytic and enantioselective C-H direct acylation of ferrocene derivatives has been developed. A series of 2-acyl-1-dimethylaminomethylferrocenes with planar chirality were provided under highly efficient and concise one-pot conditions with up to 85% yield and 98% ee. The products obtained could be easily converted to various chiral ligands via diverse transformations.
- Pi, Chao,Cui, Xiuling,Liu, Xiuyan,Guo, Mengxing,Zhang, Hanyu,Wu, Yangjie
-
supporting information
p. 5164 - 5167
(2014/12/11)
-
- Enantioselective oxidation of 1,2-diols with quinine-derived urea organocatalyst
-
Quinine-derived urea has been identified as a highly efficient organocatalyst for the enantioselective oxidation of 1,2-diols using bromination reagents as the oxidant. This simple procedure utilizes readily available reagents and operates at ambient temperature to yield a wide range of α-hydroxy ketones in good yield (up to 94%) and excellent enantioselectivity (up to 95% ee).
- Rong, Zi-Qiang,Pan, Hui-Jie,Yan, Hai-Long,Zhao, Yu
-
supporting information
p. 208 - 211
(2014/01/23)
-
- Conjugated polymers as photoredox catalysts: Visible-light-driven reduction of aryl aldehydes by poly(p-phenylene)
-
The use of visible light in photocatalysis has been intensively studied because of its natural abundance, ease of use, and promising potential for industrial applications. However, there are several challenges to utilizing visible light for organic functional group transformations. These challenges include the low absorptivity of most organic compounds in the visible spectrum, and side reactions are often prevalent in photochemical reactions. Visible-light-sensitive catalysts offer a means to overcome these obstacles. Conjugated polymers are semiconductors that offer a large range of redox potentials, they are stable, and they often absorb visible light. Despite these desirable properties for photocatalysis, only a limited number of organic reactions utilizing conjugated polymers as photocatalysts have been reported. In one such example, poly(p-phenylene) was used to induce the pinacol coupling reaction of benzaldehyde upon irradiation with visible light. In this work, visible light, thiols, and poly(p-phenylene) were employed to reduce aryl aldehydes to their respective alcohols to better characterize the reaction mechanisms of this system. The effects of varying reaction conditions on the rate of photocatalysis indicated interfacial electron transfer from the poly(p-phenylene) surface to the substrate as the initial productive step. Additionally, the chemoselective reduction of aryl aldehydes over aryl ketones and alkyl aldehydes was achieved with this system.
- Zhang, Miao,Rouch, William D.,McCulla, Ryan D.
-
supporting information
p. 6187 - 6196
(2013/01/15)
-
- A convenient synthesis of unsymmetrical pinacols by coupling of structurally similar aromatic aldehydes mediated by low-valent titanium
-
The one-pot, selective cross pinacol-type couplings between two structurally similar aromatic aldehydes promoted by low-valent titanium generated unsymmetrical pinacols in moderate to good isolated yields in an erythrolthreo ratio of up to 91:9. This synt
- Duan, Xin-Fang,Feng, Jian-Xia,Zi, Guo-Fu,Zhang, Zhan-Bin
-
experimental part
p. 277 - 282
(2009/06/24)
-
- Reaction of secondary and tertiary aliphatic halides with aromatic aldehydes mediated by chromium(II): a selective cross-coupling of alkyl and ketyl radicals
-
Takai-Utimoto reactions with secondary and tertiary aliphatic halides usually failed according to previous reports. Now, significant improvements could be achieved, and especially secondary aliphatic halides can be coupled to aromatic aldehydes in yields of up to >95%. A variety of processes are competing with the desired one, and thus conditions must be adapted to the nature of the aldehyde as well as the aliphatic halide used, as the outcome of these reactions is strongly affected by the putative radical intermediates.
- Wessjohann, Ludger A.,Schmidt, Gisela,Schrekker, Henri S.
-
p. 2134 - 2142
(2008/09/18)
-
- A novel nickel(0)-catalyzed cascade Ullmann-pinacol coupling: From o-bromobenzaldehyde to trans-9,10-dihydroxy-9,10-dihydrophenanthrene
-
Using 5 mol% of (Ph3P)2NiCl2 as a catalyst, Zn powder as a reductant, ortho-carbonyl-substituted aryl halides could be coupled to form trans-9,10-dihydroxy-9,10-dihydrophenanthrenes in a one-pot cascade reaction. Georg Thieme Verlag Stuttgart.
- Lin, Shuang-Zheng,Chen, Qing-An,You, Tian-Pa
-
p. 2101 - 2105
(2008/02/09)
-
- Development of a catalytic electron transfer system mediated by transition metal ate complexes: Applicability and tunability of electron-releasing potential for organic transformations
-
We have developed a catalytic electron transfer (ET) system composed of a transition metal ate complex (Me3M(II)Li; M = Co(II), Mn(II), Fe(II)) and magnesium. This system (catalytic Me3M(II)Li/Mg) turned out to be effective for various ET reactions, such as the desulfonylation of N-phenylsulfonyl amides, and others (the chemoselective cleavage of O-allyl groups, the reduction of nitro groups, the partial reduction of diketones, and the reductive coupling of diphenyliodonium salt). The ET ability of this system can be tuned by changing the ligands of the ate complexes. This tunability was experimentally and electrochemically demonstrated: alkoxy-ligated and dianion-type ET ate complexes showed attenuated and enhanced reducing abilities, respectively. The modification of the ET abilities was evaluated by means of electrochemical measurements and chemical reactions. These results provide a basis for the design of various tailor-made ET ate complexes.
- Uchiyama, Masanobu,Matsumoto, Yotaro,Nakamura, Shinji,Ohwada, Tomohiko,Kobayashi, Nagao,Yamashita, Natsuno,Matsumiya, Atsushi,Sakamoto, Takao
-
p. 8755 - 8759
(2007/10/03)
-
- CeCl3/Sm promoted pinacolic coupling of aromatic aldehydes and ketones
-
The pinacolic coupling of aromatic aldehydes and ketone was performed with cerium trichloride and samarium in THF at room temperature to afford the corresponding 1,2-diols in good yields.
- Li, Xue,Zhang, Songlin,Zhang, Xinying,Wang, Xiao Yang
-
p. 1043 - 1045
(2007/10/03)
-
- Indium-catalyzed cross-coupling reactions between α,β -unsaturated carbonyl compounds and aromatic aldehydes
-
Cross-coupling reactions between α,β-unsaturated carbonyl compounds and aromatic aldehydes have been achieved in tetrahydrofuran (THF) at 25 °C under N2 using a catalytic amount of InCl3 (0. 05 molar amount to the substrate) in the presence of both chlorotrimethylsilane (TMSCl) and aluminum foil (Al). These reactions provide the corresponding β,γ-unsaturated ketones in moderate yields, together with pinacol-coupling products of aldehydes as side products. Chlorides other than TMSCl and AlCl3, such as LiCl, CaCl2, MgCl2, and SOCl2, are not effective at all. Without either TMSCl or Al, no reaction proceeds even in the presence of the catalyst.
- Ohe, Toshiyuki,Ohse, Takuya,Mori, Kenji,Ohtaka, Seiji,Uemura, Sakae
-
p. 1823 - 1827
(2007/10/03)
-
- A highly dl-stereoselective pinacolization of aromatic aldehydes mediated by TiCl4-Zn
-
Reduction of TiCl4(THF)4 with Zn in CH2Cl2 gave a green solution, which was found to promote the reductive coupling of aromatic aldehydes to yield 1,2-diols with high threo selectivity.
- Li, Tingyou,Cui, Wei,Liu, Jigang,Zhao, Jianzhang,Wang, Zongmu
-
p. 139 - 140
(2007/10/03)
-
- Improved synthesis and crystal structure of TiCl3(tmeda)(thf): A highly stereoselective pinacol coupling reagent for aromatic aldehydes
-
A monomeric titanium(III) complex, TiCl3(tmeda)(thf) (1), has been prepared by a reaction of TiCl4 with TMEDA, Zn, and a catalytic amount of PbCl2 in an almost quantitative yield. The solid state structure of 1 is revealed by X-ray crystallographic analysis. The complex 1 couples aromatic aldehydes under mild conditions to give 1,2-diols in good to excellent yields with high d/-selectivities.
- Oshiki, Toshiyuki,Kiriyama, Takayuki,Tsuchida, Kazuaki,Takai, Kazuhiko
-
p. 334 - 335
(2007/10/03)
-
- Magnesium-mediated carbon-carbon bond formation in aqueous media: Barbier-Grignard allylation and pinacol coupling of aldehydes
-
Magnesium-mediated Barbier-Grignard type alkylation of aldehydes with alkyl halides was studied in aqueous media. The reaction of aromatic aldehydes with allyl halides is highly effective with either THF or water as the reaction solvent but poor in a mixture of THF/water. It was found that the magnesium-mediated allylation of aldehydes with allyl bromide and iodide proceeds effectively in aqueous 0.1 N HCl or 0.1 N NH4Cl. Aromatic aldehydes reacted chemoselectively in the presence of aliphatic aldehydes. An exclusive selectivity was also observed when both aliphatic and aromatic aldehyde functionalities are present in the same molecule. In the absence of allyl halides, aldehydes and ketones reacted with magnesium in aqueous 0.1 N NH4Cl to form the corresponding pinacol coupling products in high yields. The effectiveness of the pinacol reaction was strongly influenced by the steric environment surrounding the carbonyl group. Aliphatic aldehydes and simple alkyl halides appear inert under the reaction conditions for either alkylation or the pinacol coupling reaction.
- Zhang, Wen-Chun,Li, Chao-Jun
-
p. 3230 - 3236
(2007/10/03)
-
- The first catalytic enantioselective Nozaki-Hiyama reaction
-
The Nozaki-Hiyama reaction can be performed in an enantioselective catalytic way! The catalytic system utilizes 10 mol % of an inexpensive chiral [Cr(salen)] complex. The [Cr(salen)]/Mn/Me3SiCl system effectively promotes the enantioselective addition of allyl chloride to aliphatic and aromatic aldehydes at room temperature (65-89% ee, 40-60% yield).
- Bandini, Marco,Cozzi, Pier Giorgio,Melchiorre, Paolo,Umani-Ronchi, Achille
-
p. 3357 - 3359
(2007/10/03)
-
- Sm(Hg) promoted pinacolic coupling of aromatic aldehydes and ketones
-
The pinacolic coupling of aromatic aldehydes and ketones was performed with samarium/mercury amalgam in THF at room temperature to afford the corresponding 1,2-diols in good yields.
- Wang, Lei,Zhang, Yongmin
-
p. 3991 - 3997
(2007/10/03)
-
- Magnesium in water: Simple and effective for pinacol-coupling
-
A simple and effective pinacol-coupling has been carried out with magnesium. The reaction is highly effective in water in the presence of a catalytic amount of ammonium chloride. Under these conditions, various aromatic aldehydes and ketones undergo carbonyl coupling, generating 1,2-diols in good yields. The effectiveness of the reaction is strongly influenced by the steric environment surrounding the carbonyl group. Aliphatic aldehydes appear inert under the reaction conditions.
- Zhang, Wen-Chun,Li, Chao-Jun
-
p. 3131 - 3132
(2007/10/03)
-
- Indium mediated pinacol coupling reaction of aromatic aldehydes in aqueous media
-
The carbon-carbon bond formation reaction of aromatic carbonyl compounds was performed with indium in neutral aqueous media using sonification affording the corresponding diols in moderate to good yields.
- Lim, Hwan Jung,Keum, Gyochang,Kang, Soon Bang,Chung, Bong Young,Kim, Youseung
-
p. 4367 - 4368
(2007/10/03)
-
- Reductive Coupling of Aromatic Carbonyl Compounds to Pinacols Using Zinc Powder in Aqueous Media
-
Zinc-mediated reductive coupling of aromatic carbonyl compounds occurs to give corresponding 1,2-diols in moderate to good yields in saturated NH4Cl(aq)-THF solution at room temperature.
- Wang, Lei,Sun, Xinghua,Zhang, Yongmin
-
p. 336 - 337
(2007/10/03)
-
- Electrosyntheses from aromatic aldehydes in a flow cell. Part II. The cross-coupling of benzaldehydes to unsymmetrical diols
-
It is demonstrated that the reduction of mixtures of two benzaldehydes in acidic water-methanol in a membrane flow cell with a lead cathode can lead to a mixture of diols including the unsymmetrical diol, e.g. 4-F-C6H4-CH(OH)-CH(OH)-C6H5. In the conditions employed, the ratio of the three diol products follows the statistical distribution expected for the coupling of two different radical intermediates produced in the same ratio as the concentrations of their precursors. The yield and current efficiency for the diols are excellent when the pH and potential are selected so that a 1e- reduction of both benzaldehydes occurs. The yield of unsymmetrical dimer based on one reactant can be increased substantially by using the other carbonyl compound as a sacrificial reagent. Acta Chemica Scandinavica 1998.
- Guena, Thierry,Pletcher, Derek
-
-
- Pinacolic coupling of aromatic carbonyl compounds using Zn powder in aqueous basic media without organic solvents
-
Treatment of aromatic carbonyl compounds with Zn powder in 10% aq NaOH solution without using any organic solvents under the mild conditions afforded the corresponding 1,2-diols in good yields.
- Tsukinoki, Takehito,Kawaji, Takatoshi,Hashimoto, Iwao,Mataka, Shuntaro,Tashiro, Masashi
-
p. 235 - 236
(2007/10/03)
-
- Magnesium- and Titanium-induced Reductive Coupling of Carbonyl Compounds: Efficient Syntheses of Pinacols and Alkenes
-
Finely dispersed magnesium on graphite was found to be a totally selective single-electron transfer reagent of general utility for the reduction of various kinds of carbonyl and dicarbonyl compounds to pinacols, a reaction quite compatible with a number of functional groups.Similarly, titanium on graphite proved to be a universally applicable reducing agent for the efficient conversion of pinacols, carbonyl and dicarbonyl compounds into alkenes and cycloalkenes respectively and for the cyclization of oxo alkanoates to enol ethers, facilitating and unifying the highly useful McMurry reaction.The practicability of the presently known carbonyl coupling methods is discussed in the light of these results.
- Fuerstner, Alois,Csuk, Rene,Rohrer, Christian,Weidmann, Hans
-
p. 1729 - 1734
(2007/10/02)
-