- Stereodivergent Pd/Cu Catalysis for the Dynamic Kinetic Asymmetric Transformation of Racemic Unsymmetrical 1,3-Disubstituted Allyl Acetates
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A stereodivergent Pd/Cu catalyst system has been developed for the unprecedented dynamic kinetic asymmetric transformation (DyKAT) of racemic unsymmetrical 1,3-disubstituted allylic acetates with prochiral aldimine esters. A series of α,α-disubstituted α-amino acids bearing vicinal stereocenters were easily prepared with excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >20:1 dr). Moreover, all four stereoisomers of the product can be readily obtained simply by switching the configurations of the two chiral metal catalysts. Furthermore, the present work highlights the power of synergistic Pd/Cu catalysis consisting of two common bidentate chiral ligands for stereodivergent synthesis.
- He, Rui,Huo, Xiaohong,Zhao, Ling,Wang, Feijun,Jiang, Liyin,Liao, Jian,Zhang, Wanbin
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p. 8097 - 8103
(2020/05/22)
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- Biocatalytic Enantioselective Oxidation of Sec-Allylic Alcohols with Flavin-Dependent Oxidases
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The oxidation of allylic alcohols is challenging to perform in a chemo- as well as stereo-selective fashion at the expense of molecular oxygen using conventional chemical protocols. Here, we report the identification of a library of flavin-dependent oxidases including variants of the berberine bridge enzyme (BBE) analogue from Arabidopsis thaliana (AtBBE15) and the 5-(hydroxymethyl)furfural oxidase (HMFO) and its variants (V465T, V465S, V465T/W466H and V367R/W466F) for the enantioselective oxidation of sec-allylic alcohols. While primary and benzylic alcohols as well as certain sugars are well known to be transformed by flavin-dependent oxidases, sec-allylic alcohols have not been studied yet except in a single report. The model substrates investigated were oxidized enantioselectively in a kinetic resolution with an E-value of up to >200. For instance HMFO V465S/T oxidized the (S)-enantiomer of (E)-oct-3-en-2-ol (1 a) and (E)-4-phenylbut-3-en-2-ol with E>200 giving the remaining (R)-alcohol with ee>99% at 50% conversion. The enantioselectivity could be decreased if required by medium engineering by the addition of cosolvents (e. g. dimethyl sulfoxide).
- Gandomkar, Somayyeh,Jost, Etta,Loidolt, Doris,Swoboda, Alexander,Pickl, Mathias,Elaily, Wael,Daniel, Bastian,Fraaije, Marco W.,Macheroux, Peter,Kroutil, Wolfgang
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supporting information
p. 5264 - 5271
(2019/11/13)
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- A catalytic allylic cation-induced intermolecular allylation-semipinacol rearrangement
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A catalytic intermolecular semipinacol rearrangement induced by allylic carbocations has been realized. This tandem reaction is highly efficient under the catalysis of ZnBr2, generating a wide range of α-homoallyl substituted ketones which contain all-carbon quaternary centres in good to excellent yields (up to 98%) with moderate to high diastereoselectivities (up to >20?:?1). Synthetic application of this novel methodology in the construction of core structures of natural products is also reported.
- Xu, Ming-Hui,Dai, Kun-Long,Tu, Yong-Qiang,Zhang, Xiao-Ming,Zhang, Fu-Min,Wang, Shao-Hua
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p. 7685 - 7688
(2018/07/15)
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- Chemo-, regio-, and stereoselective Heck-Matsuda arylation of allylic alcohols under mild conditions
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Heck arylation with allylic alcohol is extremely challenging due to chemo-, regio-, and stereoselective scrambling. Here we report a mild protocol for the alcohol selective β- and α-arylation of allylic and cinnamyl alcohols respectively with aryldiazonium salts. The steric and electronic parameters of the alkene play a prominent role in the regioselectivity.
- Chaudhari, Tohasib Yusub,Hossian, Asik,Manna, Manash Kumar,Jana, Ranjan
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supporting information
p. 4841 - 4845
(2015/05/05)
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- Copper-catalyzed oxidative alkenylation of C(sp3)-H bonds via benzyl or alkyl radical addition to β-nitrostyrenes
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A new method for the preparation of (E)-β-alkylstyrene derivatives has been developed via the addition of a benzyl or alkyl radical to β-nitrostyrenes using di-tert-butyl peroxide (DTBP) as the oxidant in the presence of Cu powder catalyst. The C-H bonds in various toluene derivatives, ethers, alkanes and alcohols were successfully converted into C-C bonds to yield the corresponding (E)-β-alkylstyrene derivatives in moderate to good yields.
- Guo, Shengrong,Yuan, Yanqin,Xiang, Jiannan
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supporting information
p. 3093 - 3097
(2015/04/14)
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- Facile synthesis of Z -alkenes via uphill catalysis
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Catalytic access to thermodynamically less stable Z-alkenes has recently received considerable attention. These approaches have relied upon kinetic control of the reaction to arrive at the thermodynamically less stable geometrical isomer. Herein, we present an orthogonal approach which proceeds via photochemically catalyzed isomerization of the thermodynamic E-alkene to the less stable Z-isomer which occurs via a photochemical pumping mechanism. We consider two potential mechanisms. Importantly, the reaction conditions are mild, tolerant, and operationally simple and will be easily implemented.
- Singh, Kamaljeet,Staig, Shannon J.,Weaver, Jimmie D.
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p. 5275 - 5278
(2014/05/06)
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- Heck-Matsuda reaction of arenediazonium salts in water
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The palladium-catalyzed arylation of alkenes with aryldiazonium salts can be carried out through an environmentally friendly protocol using neat water low palladium loadings at room temperature under base-additive- and ligand-free conditions.
- Salabert, Jordi,Sebastián, Rosa María,Vallribera, Adelina,Cívicos, José Francisco,Nájera, Carmen
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p. 2655 - 2659
(2013/03/28)
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- Synthesis and anticancer activity of novel halolactones with β-aryl substituents from simple aromatic aldehydes
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A series of 20 novel racemic iodo-, bromo- and chlorolactones, possessing β-phenyl-γ-lactone or β-phenyl-δ-lactone framework, were synthesized from commercially available aromatic aldehydes in convenient five-step syntheses. Some of them showed noticeable cytotoxic effect against two cancer lines, Jurkat (human leukaemia) and D17 (canine osteosarcoma). The highest activity, comparable with carboplatin, was observed for cis-5-(1-iodoethyl)-4-(4′-isopropylphenyl)dihydrofuran-2-one against Jurkat cell line.
- G?adkowski, Witold,Skrobiszewski, Andrzej,Mazur, Marcelina,Siepka, Monika,Pawlak, Aleksandra,Obmińska-Mrukowicz, Bozena,Bia?on?ska, Agata,Poradowski, Dominik,Drynda, Angelika,Urbaniak, Mariusz
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p. 10414 - 10423
(2013/11/19)
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- Allylic activation across an Ir-Sn heterobimetallic catalyst: Nucleophilic substitution and disproportionation of allylic alcohol
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A nucleophilic substitution of allylic alcohols with carbon (arene, heteroarene, allyltrimethylsilane, and 1,3-dicarbonyl compound), sulfur (thiol), oxygen (alcohol), and nitrogen (sulfonamide) nucleophiles has been demonstrated using an in house developed [Ir(COD)(SnCl3)l(μ-Cl)]2 heterobimetallic catalyst in 1,2-dichloroethane to afford the corresponding allylic products in moderate to excellent yields. In 4-hydroxycoumarin, allylation occurs at the 3-position. The diaryl-substituted allylic alcohols undergo disproportionation in presence of the heterobimetallic catalyst to provide the corresponding alkenes and chalcones. An electrophilic mechanism is proposed from Hammett correlation study.
- Chatterjee, Paresh Nath,Roy, Sujit
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p. 3776 - 3785
(2012/07/14)
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- Chemoselective conjugate reduction of α,β-unsaturated ketones catalyzed by rhodium amido complexes in aqueous media
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Although a notable feature of Noyori's Ru-TsDPEN complex is that the transfer hydrogenation reaction is highly chemoselective for the C-O functional group and tolerant of alkenes, our early report indicated that the chemoselectivity could be switched from C-O to C-C bonds in the transfer hydrogenation of activated α,β-unsaturated ketones. Now we have found that a variety of α,β-unsaturated ketones, even without other electron-withdrawing functional groups, could be reduced on the alkenic double bonds with high selectivities employing amido-rhodium hydride complex in aqueous media, and up to 100% chemoselectivity has been achieved. It is notable that the chemoselectivity was improved significantly on going from organic solvent to water. Moreover, a 1,4-addition mechanism has been proposed on the basis of the corresponding experimental details and computational analysis.
- Li, Xuefeng,Li, Liangchun,Tang, Yuanfu,Zhong, Ling,Cun, Linfeng,Zhu, Jin,Liao, Jian,Deng, Jingen
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supporting information; experimental part
p. 2981 - 2988
(2010/07/05)
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- Free-radical-initiated coupling reaction of alcohols and alkynes: Not co but C-C bond formation
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This work demonstrates an efficient method to prepare allylic alcohols via direct C-C bond formation using electron-rich alkynes and aliphatic alcohols initiated by tert-butyl hydroperoxide.
- Liu, Zhong-Quan,Sun, Liang,Wang, Jian-Guo,Han, Jie,Zhao, Yan-Kai,Zhou, Bo
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supporting information; scheme or table
p. 1437 - 1439
(2009/09/07)
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- Enantiomerically pure allylic alcohols: preparation by Candida parapsilosis ATCC 7330 mediated deracemisation
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Biocatalytic deracemisation of racemic allylic alcohols by whole cells of Candida parapsilosis ATCC 7330 resulted in the formation of the (R)-enantiomers in high enantiomeric excesses (up to >99%) and isolated yields (up to 79%).
- Titu, Devamani,Chadha, Anju
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p. 1698 - 1701
(2008/12/20)
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- A chiral electrophilic selenium reagent to promote the kinetic resolution of racemic allylic alcohols
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(Chemical Equation Presented) The first example of a kinetic resolution process promoted by electrophilic selenium reagents is reported. Racemic allylic alcohols react with half equivalents of a selenenylating agent in methanol leading to the regiospecific formation of the corresponding addition products with a very high level of facial selectivity (from 95:5 to 98:2 dr). The unreacted alcohols can be recovered in an optically enriched form (from 90 to 94% ee).
- Tiecco, Marcello,Testaferri, Lorenzo,Santi, Claudio,Tomassini, Cristina,Bonini, Rosaria,Marini, Francesca,Bagnoli, Luana,Temperini, Andrea
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p. 4751 - 4753
(2007/10/03)
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- A stereoselective synthesis of unsaturated phosphonates by Wittig-Horner reactions of bisphosphonylmethane with 5-aryl-(3-methyl)-2E,4E-pentadienals
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A new type of unsaturaled phosphonates 5 were synthesized by the Wittig-Horner reactions of bisphosphonylmethane 4 with 5-aryl-2(E),4(E)-pentadienal and 5-aryl-3-methyl-2(E), 4(E)-pentadienal. The structures of all new compounds prepared were characterize
- Shi, De Qing,Chen, Ru Yu
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p. 229 - 237
(2007/10/03)
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- Ruthenium-catalyzed isomerization of homoallylic alcohols in water
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Through the catalysis of RuCl2(PPh3)3, the functional groups of homoallylic alcohols are repositioned to give allylic alcohols with controlled regioselectivity. The reaction proceeds most efficiently in an aqueous media. The selectivity in product formation is affected by the reaction temperature and the amount of the catalyst being used. A higher reaction temperature and the use of a smaller amount of the catalyst are preferable for the formation of allylic alcohols. The reaction process was postulated as a tandem olefin migration-allylic rearrangement. Under the same reaction conditions, the functional groups of allylic alcohols undergo allylic rearrangements.
- Wang, Dong,Chen, Dongli,Haberman, John X.,Li, Chao-Jun
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p. 5129 - 5142
(2007/10/03)
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