- Rhodium-catalyzed asymmetric hydrogenation of exocyclic α,β-unsaturated carbonyl compounds
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A highly enantioselective hydrogenation of exocyclic α,β-unsaturated carbonyl compounds catalyzed by Rh/bisphosphine-thiourea (ZhaoPhos) has been developed, giving the corresponding α-chiral cyclic lactones, lactams and ketones with high yields and excellent enantioselectivities (up to 99% yield and 99% ee). Remarkably, the hydrogen bond between the substrate and the catalyst plays a critical role in this transformation. The synthetic utility of this protocol has been demonstrated by efficient synthesis of chiral 3-(4-fluorobenzyl)piperidine, a key chiral fragment of bioactive molecules.
- Yang, Jiaxin,Li, Xiuxiu,You, Cai,Li, Shuailong,Guan, Yu-Qing,Lv, Hui,Zhang, Xumu
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supporting information
p. 856 - 859
(2020/02/15)
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- Copper-Catalyzed Desaturation of Lactones, Lactams, and Ketones under pH-Neutral Conditions
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A copper-catalyzed desaturation method that is suitable for converting lactones, lactams, and cyclic ketones to their α,β-unsaturated counterparts is reported. The reaction does not require strong base/acid or sulfur/selenium reagents and can be carried out through a simple one-step operation. The protocol uses inexpensive catalysts and reagents and exhibits excellent scalability and functional group tolerance. Notably, tert-butyl alcohol is the only stoichiometric byproduct produced, and overoxidation is not observed. The reaction mechanism has been investigated through control experiments, deuterium labeling, radical clock, electron paramagnetic resonance, high-resolution mass spectrometry, and kinetic studies. The data obtained are consistent with a reaction pathway involving reversible α-deprotonation by a Cu(II)-OtBu species followed by further oxidation of the resulting Cu enolate.
- Chen, Ming,Dong, Guangbin
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supporting information
p. 14889 - 14897
(2019/10/02)
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- Unprecedented E-stereoselectivity on the sigmatropic Hurd-Claisen rearrangement of Morita-Baylis-Hillman adducts: A joint experimental-theoretical study
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Herein we report the first systematic investigation of the tandem mercury(ii) catalysed transvinylation/Hurd-Claisen rearrangement of MBH adducts derived from alkyl acrylates. This is the first report of E-selectivity for MBH adducts with alkyl side chain
- Silva, Vinicius Sobral,Tolentino, Terezinha Alves,Rodrigues, Tiago Costa Alves Fontoura,Santos, Fernanda Ferrari Martins,Machado, Daniel Francisco Scalabrini,Silva, Wender Alves,Oliveira, Heibbe Cristhian Benedito De,Machado, Angelo Henrique Lira
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p. 4498 - 4511
(2019/05/17)
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- Bioactivity-guided mixed synthesis and evaluation of α-alkenyl-γ and δ-lactone derivatives as potential fungicidal agents
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In view of the great antifungal activities of sesquiterpene lactones and natural product Tulipalin A, 52 derivatives derived from α-methylene-γ-butyrolactone substructures were synthesized to study antifungal activities. In vitro and in vivo antifungal activity results revealed that compounds 2-25, which contain a γ-butyrolactone scaffold and cinnamic aldehyde moiety, have greater potent fungicidal activity than other compounds. The preliminary structure-activity relationships (SARs) demonstrated that compounds with electron-withdrawing groups and small steric hindrance would have more desirable potency. Meanwhile, the quantitative structure-activity relationship (QSAR) model (R2 = 0.947, F = 65.77, and S2 = 0.0028) revealed a convincing correlation of antifungal activity against B. cinerea with molecular structures of title compounds. The present study provided a more detailed insight into the antifungal activity of the α-methylene-γ-butyrolactone substructure, which provided a potential expectation for the exploration of α-alkenyl-γ-butyrolactone structures in agriculture.
- Wu, Yong-Ling,Gao, Yan-Qing,Wang, De-Long,Zhong, Chen-Quan,Feng, Jun-Tao,Zhang, Xing
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p. 56496 - 56508
(2017/12/27)
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- Electrophilicities of benzaldehyde-derived iminium ions: Quantification of the electrophilic activation of aldehydes by iminium formation
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Rate constants for the reactions of benzaldehyde-derived iminium ions with C-nucleophiles (enamines, silylated ketene acetals, and enol ethers) have been determined photometrically in CH3CN solution and used to determine the electrophilicity pa
- Appel, Roland,Chelli, Saloua,Tokuyasu, Takahiro,Troshin, Konstantin,Mayr, Herbert
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p. 6579 - 6587
(2013/06/26)
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- Custom synthesis of substituted butenolides, dihydropyranones, and α-E-alkylidenelactones via alkenylalumination
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Alkenylalumination of aldehydes with [α-(ethoxycarbonyl)-β-(t- butyldimethylsilyloxyalkyl)alkenyl]diisobutylaluminum provides the corresponding α-Z-alkylidene-β′-hydroxy esters, which upon protection and treatment with trifluoroacetic acid lactonizes to f
- Veeraraghavan Ramachandran,Pratihar, Debarshi,Garner, Garrett,China Raju
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p. 4985 - 4988
(2011/10/08)
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- Iridium-catalyzed highly enantioselective hydrogenation of exocyclic α,β-unsaturated carbonyl compounds
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By using the iridium complex of a phosphine-oxazoline ligand with an axis-unfixed biphenyl backbone, a highly enantioselective hydrogenation of the C=C bond of exocyclic α,β-unsaturated carbonyl compounds to afford α-chiral cyclic ketones, lactones and lactams was developed.
- Tian, Fengtao,Yao, Dongmei,Liu, Yuanyuan,Xie, Fang,Zhang, Wanbin
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supporting information; experimental part
p. 1841 - 1845
(2010/10/21)
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- Titanium-mediated carboxylation of alkynes with carbon dioxide
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The regioselective carboxylation of nonactivated internal alkynes can be performed with carbon dioxide under atmospheric pressure using a simple procedure based on the chemistry of Sato-type diisopropyloxytitanacyclopropenes. Various polysubstituted vinylcarboxylic acids and butenolides can be prepared in this way. In addition, this paper describes an experimental protocol for the preparation of solutions of (η2-cyclopentene)diisopropyloxytitanium. This complex also reacts with carbon dioxide, and mediates pinacol coupling of acetophenone. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Six, Yvan
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p. 1157 - 1171
(2007/10/03)
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- Synthesis of γ- and δ-Lactones by Free-Radical Annelation of Se-Phenyl Selenocarbonates
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A general method for the synthesis of γ- and δ-lactones through the intramolecular addition of alkoxycarbonyl radicals, formed by reaction of Se-phenylselenocarbonates with n-Bu3SnH, onto carbon-carbon multiple bonds is described.This free-radical cyclization is characterized by high regioselectivity favoring exo addition and by a high ratio of cyclization to reduction.Monocyclic, fused bicyclic, and spirocyclic lactones are formed in good to excellent yield.Use of allyltri-n-butyltin as a chain-transfer agent in the place of n-Bu3SnH affords the corresponding 3-butenyl lactones.
- Bachi, Mario D.,Bosch, Eric
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p. 4696 - 4705
(2007/10/02)
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