- Development of Enantiospecific Coupling of Secondary and Tertiary Boronic Esters with Aromatic Compounds
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The stereospecific cross-coupling of secondary boronic esters with sp2 electrophiles (Suzuki-Miyaura reaction) is a long-standing problem in synthesis, but progress has been achieved in specific cases using palladium catalysis. However, related couplings with tertiary boronic esters are not currently achievable. To address this general problem, we have focused on an alternative method exploiting the reactivity of a boronate complex formed between an aryl lithium and a boronic ester. We reasoned that subsequent addition of an oxidant or an electrophile would remove an electron from the aromatic ring or react in a Friedel-Crafts-type manner, respectively, generating a cationic species, which would trigger 1,2-migration of the boron substituent, creating the new C-C bond. Elimination (preceded by further oxidation in the former case) would result in rearomatization giving the coupled product stereospecifically. Initial work was examined with 2-furyllithium. Although the oxidants tested were unsuccessful, electrophiles, particularly NBS, enabled the coupling reaction to occur in good yield with a broad range of secondary and tertiary boronic esters, bearing different steric demands and functional groups (esters, azides, nitriles, alcohols, and ethers). The reaction also worked well with other electron-rich heteroaromatics and 6-membered ring aromatics provided they had donor groups in the meta position. Conditions were also found under which the B(pin)- moiety could be retained in the product, ortho to the boron substituent. This protocol, which created a new C(sp2)-C(sp3) and an adjacent C-B bond, was again applicable to a range of secondary and tertiary boronic esters. In all cases, the coupling reaction occurred with complete stereospecificity. Computational studies verified the competing processes involved and were in close agreement with the experimental observations.
- Odachowski, Marcin,Bonet, Amadeu,Essafi, Stephanie,Conti-Ramsden, Philip,Harvey, Jeremy N.,Leonori, Daniele,Aggarwal, Varinder K.
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p. 9521 - 9532
(2016/08/12)
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- Synthesis of α-Tertiary Amine Derivatives by Intermolecular Hydroamination of Unfunctionalized Alkenes with Sulfamates under Trifluoromethanesulfonic Acid Catalysis
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An efficient and mild trifluoromethanesulfonic acid-catalyzed hydroamination of unfunctionalized alkenes to afford α-tertiary amine derivatives at temperatures as low as room temperature is reported. 2,2,2-Trifluoroethyl sulfamate was found to be the optimal nitrogen source because its good solubility in both organic solvents and water facilitated both conversion and purification. The reaction conditions were compatible with a variety of substrate functional groups and afforded moderate to good yields. The desired amine compounds could be obtained easily by means of a mild, one-pot, redox-neutral deprotection procedure. Caryolane amine was synthesized with excellent chemo- and regioselectivities by means of a cascade hydroamination reaction of β-caryophyllene.
- Fei, Jun,Wang, Zhen,Cai, Zheren,Sun, Hao,Cheng, Xu
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supporting information
p. 4063 - 4068
(2016/01/25)
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- Ru(III)-Catalyzed Cyclization of Arene-Alkene Substrates via Intramolecular Electrophilic Hydroarylation
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(Matrix presented) We herein report that RuCl3/AgOTf has proven to be a hydroarylation catalyst with an efficiency and scope superior to previously known methods. This catalyst demonstrated consistent performance with arene-ene substrates of diverse structural features, providing good to excellent yields of cyclization products (chromanes, tetralins, terpenoids, dihydrocoumarins).
- Youn, So Won,Pastine, Stefan J.,Sames, Dalibor
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p. 581 - 584
(2007/10/03)
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- Efficient preparation of trisubstituted alkenes using the SmI2 modification of the Julia-Lythgoe olefination of ketones and aldehydes
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High yields of di- and tri-substituted alkenes are obtained by a modification of the Julia-Lythgoe olefination reaction involving the in situ capture of intermediate β-alkoxy-sulfones by benzoyl or trimethylsilyl chloride, followed by SmI2-mediated reductive elimination. This novel protocol also provides a connective preparation of dienyl ethers, which are important partners in Diels-Alder cycloadditions.
- Markó, István E,Murphy, Fiona,Kumps, Lucien,Ates, Ali,Touillaux, Roland,Craig, Donald,Carballares, Santiago,Dolan, Simon
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p. 2609 - 2619
(2007/10/03)
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- Efficient preparation of trisubstituted alkenes using the Julia-Lythgoe olefination of ketones. On the key-role of SmI2 in the reductive elimination step
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Modification of the Julia-Lythgoe olefination reaction between ketones and primary sulfones leads to trisubstituted alkenes in good overall yields. Samarium diiodide is shown to play a crucial role in the reductive elimination step.
- Marko, Istvan E.,Murphy, Fiona,Dolan, Simon
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p. 2089 - 2092
(2007/10/03)
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