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| 2. |
- Montesinos-Magraner, Marc, et al.
(författare)
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General Cyclopropane Assembly by Enantioselective Transfer of a Redox-Active Carbene to Aliphatic Olefins
- 2019
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 58:18, s. 5930-5935
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Tidskriftsartikel (refereegranskat)abstract
- Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates, and reagents, even when targeting similar compounds. This approach slows down discovery and limits available chemical space. Introduced herein is a practical and versatile diazocompound and its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. The redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect allowed the asymmetric cyclopropanation of various olefins, including unfunctionalized aliphatic alkenes, that enables the three-step total synthesis of (-)-dictyoptereneA. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons.
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| 3. |
- Otero-Fraga, Jorge, et al.
(författare)
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Direct and Stereospecific [3+2] Synthesis of Pyrrolidines from Simple Unactivated Alkenes
- 2017
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Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 56:42, s. 12962-12966
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Tidskriftsartikel (refereegranskat)abstract
- Pyrrolidines are important heterocyclic compounds with endless applications in organic synthesis, metal catalysis, and organocatalysis. Their potential as ligands for first-row transition-metal catalysts inspired a new method to access complex poly-heterocyclic pyrrolidines in one step from available materials. This fundamental step forward is based on the discovery of an essential organoaluminum promoter that engages unactivated and electron-rich olefins in intermolecular [3+2] cycloadditions.
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| 4. |
- Otero-Fraga, Jorge, et al.
(författare)
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Perspectives on Intermolecular Azomethine Ylide [3+2] Cycloadditions with Non-Electrophilic Olefins
- 2017
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Ingår i: Synthesis (Stuttgart). - : Georg Thieme Verlag KG. - 0039-7881 .- 1437-210X. ; 49:4, s. 802-809
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Forskningsöversikt (refereegranskat)abstract
- Our interest in the synthesis of compact nitrogen heterocycles from abundant sources has motivated a critical analysis of the status in azomethine ylide chemistry. Despite the outstanding developments in catalytic enantioselective [3+2] cycloadditions, these are still limited to electron-poor olefins. Only a few examples can be found in the literature that report on cycloadditions using non-electrophilic alkenes and those are compiled herein. With this account we aim to extract lessons and challenges that will inspire future breakthroughs in this area.
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| 5. |
- Planas, Ferran, et al.
(författare)
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Combined Experimental and Computational Study of Ruthenium N-Hydroxyphthalimidoyl Carbenes in Alkene Cyclopropanation Reactions
- 2021
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 11:17, s. 10950-10963
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Tidskriftsartikel (refereegranskat)abstract
- A combined experimental–computational approach has been used to study the cyclopropanation reaction of N-hydroxyphthalimide diazoacetate (NHPI-DA) with various olefins, catalyzed by a ruthenium-phenyloxazoline (Ru-Pheox) complex. Kinetic studies show that the better selectivity of the employed redox-active NHPI diazoacetate is a result of a much slower dimerization reaction compared to aliphatic diazoacetates. Density functional theory calculations reveal that several reactions can take place with similar energy barriers, namely, dimerization of the NHPI diazoacetate, cyclopropanation (inner-sphere and outer-sphere), and a previously unrecognized migratory insertion of the carbene into the phenyloxazoline ligand. The calculations show that the migratory insertion reaction yields an unconsidered ruthenium complex that is catalytically competent for both the dimerization and cyclopropanation, and its relevance is assessed experimentally. The stereoselectivity of the reaction is argued to stem from an intricate balance between the various mechanistic scenarios.
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