- Synthesis of the Taxol Core via Catalytic Asymmetric 1,4-Addition of an Alkylzirconium Nucleophile
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The Taxol core was prepared in five steps via a key copper-catalyzed asymmetric conjugate addition trapping sequence. The use of a bromodiene-derived alkylzirconium nucleophile followed by trapping with POCl3/DMF gave a highly functionalized intermediate featuring a quaternary center in 69% yield with 92% ee. After 1,2-addition, Suzuki-Miyaura cross-coupling, allylic oxidation, and a type II intramolecular Diels-Alder reaction, the taxol core was obtained in 11% overall yield with 92% ee.
- Wang, Jiao Yu Joseph,Fletcher, Stephen P.
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- Synthesis of Axially Chiral Styrenes through Pd-Catalyzed Asymmetric C?H Olefination Enabled by an Amino Amide Transient Directing Group
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The atroposelective synthesis of axially chiral styrenes remains a formidable challenge due to their relatively lower rotational barriers compared to the biaryl atropoisomers. Herein, we describe the construction of axially chiral styrenes through Pd
- Jin, Liang,Li, Ya,Liu, Lei,Liu, Yan-Hua,Shi, Bing-Feng,Song, Hong,Yao, Qi-Jun
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supporting information
p. 6576 - 6580
(2020/03/10)
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- Sequential O-Arylation/Lanthanide(III)-Catalyzed [3,3]-Sigmatropic Rearrangement of Bromo-Substituted Allylic Alcohols
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Lanthanide(III)-catalyzed aryl-Claisen rearrangement of substrates bearing halo-substituted allyl groups, specifically 2-bromoallyl aryl ethers, afford ortho -2-bromoallylphenols. Aryl ether substrates were synthesized from brominated allylic alcohols via Mitsunobu reaction, Cu(II)-catalyzed arylation using potassium aryltrifluoroborate salts, or S N Ar reaction. Aryl-Claisen rearrangements proceeded in moderate to excellent yields using Eu(III) catalysis. The alkenylbromide functionality remains intact, illustrating the compatibility of synthetically important alkenylhalides during C-O/C-C σ-bond migration processes. Subsequent derivatization of the ortho -2-bromoallylphenol products through O-alkylation or C-arylation/alkenylation via Suzuki-Miyaura cross-coupling demonstrate the potential to access densely-functionalized molecules.
- Ramadhar, Timothy R.,Kawakami, Jun-Ichi,Batey, Robert A.
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supporting information
p. 2865 - 2870
(2017/12/14)
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- Preparation of α-haloacrylate derivatives via dimethyl sulfoxide-mediated selective dehydrohalogenation
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(Chemical Equation Presented) Dimethyl sulfoxide causes α/β-dihalopropanoate derivatives to undergo efficient, selective dehydrohalogenation to form α-haloacrylate analogues. A variety of α-halo Michael acceptors were prepared in dimethyl sulfoxide under mild, base-free conditions, including the preparation of α-bromoacrolein and α-chloro- and bromoacrylonitriles. Synthesis of these molecules has been reported in the literature to be difficult. Among all the existing dehydrohalogenation procedures, this protocol is the most facile, practical, and environmentally benign process.
- Li, Wei,Li, Jianchang,Wan, Zhao-Kui,Wu, Junjun,Massefski, Walter
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p. 4607 - 4610
(2008/03/13)
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- Enantioselective Preparation of Polyfunctional Secondary Allylic Alcohols Using Functionalized Dialkylzincs Prepared by a Copper(I) Catalyzed Iodine-Zinc Exchange Reaction.
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Catalytic amounts of Cu(I) salts considerably facilitate the iodine-zinc exchange reaction leading to polyfunctional dialkylzincs.The catalytic asymmetric addition of these zinc reagents to a wide range of α,β-unsaturated aldehydes provides polyfunctional allylic alcohols with a high enantioselectivity.
- Rozema, Michael J.,Eisenberg, Christina,Luetjens, Henning,Ostwald, Roswitha,Belyk, Kevin,Knochel, Paul
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p. 3115 - 3118
(2007/10/02)
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