- Oxidation-Initiated Cyclizations of Pentadienyl Ethers: An Alternative Entry to the Nazarov Reaction
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Oxidation-initiated Nazarov reactions of 1,4-pentadien-3-yl ethers take place in the presence of DDQ. Termination by regioselective elimination preserves both stereocenters created during electrocyclization, providing cyclopentanone products bearing an ex
- Fradette, Ryan J.,Kang, Minkyu,West
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- Site- and Enantioselective Iridium-Catalyzed Desymmetric Mono-Hydrogenation of 1,4-Dienes
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The control of site selectivity in asymmetric mono-hydrogenation of dienes or polyenes remains largely underdeveloped. Herein, we present a highly efficient desymmetrization of 1,4-dienes via iridium-catalyzed site- and enantioselective hydrogenation. This methodology demonstrates the first iridium-catalyzed hydrogenative desymmetriation of meso dienes and provides a concise approach to the installation of two vicinal stereogenic centers adjacent to an alkene. High isolated yields (up to 96 %) and excellent diastereo- and enantioselectivities (up to 99:1 d.r. and 99 % ee) were obtained for a series of divinyl carbinol and divinyl carbinamide substrates. DFT calculations reveal that an interaction between the hydroxy oxygen and the reacting hydride is responsible for the stereoselectivity of the desymmetrization of the divinyl carbinol. Based on the calculated energy profiles, a model that simulates product distribution over time was applied to show an intuitive kinetics of this process. The usefulness of the methodology was demonstrated by the synthesis of the key intermediates of natural products zaragozic acid A and (+)-invictolide.
- Ahlquist, M?rten S. G.,Andersson, Pher G.,Nolan, Mark D.,Peters, Bram B. C.,Schulze, Erik J.,Singh, Thishana,Su, Hao,Wu, Haibo,Yang, Jianping
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supporting information
p. 19428 - 19434
(2021/07/26)
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- Natural deep eutectic solvents as an efficient and reusable active system for the Nazarov cyclization
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Natural deep eutectic solvents have emerged as alternative non-toxic, non-aqueous solvents for an increasing number of synthetic transformations. Remarkably, in some cases one (or more) components of the NaDES plays an active role in the reaction mechanism and directly participates as either a catalyst or a reagent in the reaction. In this paper, we tested several NaDESs in which one of the components is a carboxylic acid as a medium to perform the Nazarov cyclization of divinyl ketones to obtain cyclopentenones, a widespread motif in natural compounds. The reaction conditions were optimized and the scope was investigated on C-, O- A nd N-derived compounds. To assess the full sustainability of the proposed approach, the recyclability and scalability of the process were investigated, thus proving that multi-gram preparations are possible with complete recycling of the medium.
- Nejrotti, Stefano,Iannicelli, Marta,Jamil, Salwa Simona,Arnodo, Davide,Blangetti, Marco,Prandi, Cristina
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supporting information
p. 110 - 117
(2020/01/13)
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- Zeolites Catalyze the Nazarov Reaction and the tert -Butylation of Alcohols by Stabilization of Carboxonium Intermediates
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Zeolites are the most used catalysts worldwide in petrochemistry processes, with particular ability to stabilize carbocations. However, the use of zeolites in organic synthesis is still scarce. We show here that representative carboxonium-mediated organic
- Blake, Finn,Leyva-Pérez, Antonio,Sanz-Navarro, Sergio,Tejeda-Serrano, María
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p. 2031 - 2037
(2020/07/14)
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- Amine-catalyzed aldol condensation in the presence of lithium perchlorate
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A catalytic aldol condensation in the presence of lithium perchlorate and tertiary amines is described giving pure products in high yields. The aldol condensation can be performed even in the presence of hydrated lithium perchlorate. Georg Thieme Verlag Stuttgart.
- Arnold, Aline,Markert, Morris,Mahrwald, Rainer
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p. 1099 - 1102
(2007/10/03)
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