- Alkyl Ethers as Traceless Hydride Donors in Br?nsted Acid Catalyzed Intramolecular Hydrogen Atom Transfer
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A new protocol for the deoxygenation of alcohols and the hydrogenation of alkenes under Br?nsted acid catalysis has been developed. The method is based on the use of either a benzyl or isopropyl ether as a traceless hydrogen-atom donor, and involves an intramolecular hydride transfer as a key step, which is achieved in a regio- and stereoselective manner.
- Gandamana, Dhika Aditya,Wang, Bin,Tejo, Ciputra,Bolte, Benoit,Gagosz, Fabien,Chiba, Shunsuke
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p. 6181 - 6185
(2018/05/03)
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- Barbier–Negishi Coupling of Secondary Alkyl Bromides with Aryl and Alkenyl Triflates and Nonaflates
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A mild and practical Barbier–Negishi coupling of secondary alkyl bromides with aryl and alkenyl triflates and nonaflates has been developed. This challenging reaction was enabled by the use of a very bulky imidazole-based phosphine ligand, which resulted in good yields as well as good chemo- and site selectivities for a broad range of substrates at room temperature and under non-aqueous conditions. This reaction was extended to primary alkyl bromides by using an analogous pyrazole-based ligand.
- Zhang, Ke-Feng,Christoffel, Fadri,Baudoin, Olivier
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p. 1982 - 1986
(2018/02/06)
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- Terminal-Selective Functionalization of Alkyl Chains by Regioconvergent Cross-Coupling
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Hydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C?H bond functionalization methods. We describe herein a new step-economical approach that enables C?C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross-coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross-coupling then provided access to the corresponding linear arylation product in only two steps.
- Dupuy, Stéphanie,Zhang, Ke-Feng,Goutierre, Anne-Sophie,Baudoin, Olivier
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supporting information
p. 14793 - 14797
(2016/11/23)
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- Helical triskelion monophosphites as ligands in asymmetric catalysis
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Members of a new family of chiral triskelion P ligands, namely helical C3-symmetric monophos- phites P(OR)3, have been prepared in two steps Dy monoacylation of (R)- or (S)-1,1'-binaphthyl-2,2'-diol (BINOL) or diphenol using a carboxylic acid chloride followed Dy PCl3 phosphorylation. The most sterically hindered member of these monophosphites, derived from the compound accessible by monoacylation of BINOL using adamantane carboxylic acid chloride, has been characterized by X-ray crystallography and NMR spectroscopy as a single well-defined compound. It exists exclusively in the syn conformation, with a propeller-like (twisted) geometry resulting in helicity. Upon utilization of(R)- or (S)-BINOL in the two-step synthesis, the helicity proves to be P or M, respectively. When used as ligands in the Rh-catalyzed asymmetri c hydrogenation of prochiral homoallylic alcohols, these bulky helical ligands lead to respectable enantioselectivities (79-98percent ee). In contrast, the less sterically congested and more flexible BINOL-derived phenyl analogue exists in several conformeric forms, even in the crystal, and this leads to poor enantioselectivity in the model reactions (ee = 32percent). For the purpose of structural comparison, the analogous monophosphites derived from diphenol were also prepared and characterized. These compounds, again in contrast to the BINOL-derived adamantyl derivatives, occur in several different conformeric states.
- Reetz, Manfred T.,Guo, Hongchao,Jun-An, Ma.,Goddard, Richard,Mynott, Richard J.
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supporting information; experimental part
p. 4136 - 4142
(2009/09/05)
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- Amino-, mercapto- and -oxy-substituted-phenyl and -phenalkyl imidazoles
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Compounds of the formula STR1 wherein Z is a direct bond or alkylene of 1 - 3 carbon atoms which is unsubstituted or substituted on the carbon atom alpha to the phenyl group by alkyl or unsubstituted or substituted phenyl, R2 and R3 singly are H, alkyl, alkoxy, alkylmercapto, halo, nitro or, collectively, C4 H4, and R4 is alkenyl, alkinyl, unsubstituted or substituted phenyl or phenylalkyl, or, when Z is substituted methylene, also alkyl, are useful in combating Germatophyte infections, especially Trichophyton rubrum and mentagrophytes, and yeast infections, especially Candida albicans, as well as bacterial and fungal infections.
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