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Tomas Martin - One of the best experts on this subject based on the ideXlab platform.
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intramolecular Nicholas Reaction enables the stereoselective synthesis of strained cyclooctynes
Molecules, 2021Co-Authors: Diego M Monzon, Miguel A. Ramirez, Víctor S. Martín, Tomas Martin, Juan Manuel Betancort, David Diaz DiazAbstract:Cyclic products can be obtained through the intramolecular version of the Nicholas Reaction, which requires having the nucleophile connected to the alkyne unit. Here, we report the synthesis of 1-oxa-3-cyclooctynes starting from commercially available (1R,3S)-camphoric acid. The strategy is based on the initial preparation of propargylic alcohols, complexation of the triple bond with Co2(CO)8, and treatment with BF3·Et2O to induce an intramolecular Nicholas Reaction with the free hydroxyl group as nucleophile. Finally, oxidative deprotection of the alkyne afforded the cyclooctynes in good yields. Notably, large-sized R substituents at the chiral center connected to the O atom were oriented in such a way that steric interactions were minimized in the cyclization, allowing the formation of cyclooctynes exclusively with (R) configuration, in good agreement with theoretical predictions. Moreover, preliminary studies demonstrated that these cyclooctynes were reactive in the presence of azides yielding substituted triazoles.
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β hydroxy γ lactones as nucleophiles in the Nicholas Reaction for the synthesis of oxepene rings enantioselective formal synthesis of isolaurepinnacin i and rogioloxepane a ii
ChemInform, 2014Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Nuria Ortega, Tomas MartinAbstract:The key steps consist of an intermolecular Nicholas Reaction with a β-hydroxy-γ-lactone as a nucleophile and a ring closing metathesis Reaction.
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expedient synthesis of c3 symmetric hexasubstituted benzenes via Nicholas Reaction 2 2 2 cycloaddition new platforms for molecular recognition
ChemInform, 2014Co-Authors: Romen Carrillo, Tomas Martin, Matias Lopezrodriguez, Fernando Pinacho R CrisostomoAbstract:The new method is based on the Nicholas Reaction giving dimer (II) and macrocycle (III) which is further converted into the target compound by decomplexation and [2 + 2 + 2] cycloaddition under microwave irradiation.
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β hydroxy γ lactones as nucleophiles in the Nicholas Reaction for the synthesis of oxepene rings enantioselective formal synthesis of isolaurepinnacin and rogioloxepane a
Chemical Communications, 2014Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Tomas Martin, Nuria OrtegaAbstract:The enantioselective formal synthesis of (−)-isolaurepinnacin and (+)-rogioloxepane A has been achieved. The key steps are an intermolecular Nicholas Reaction with a β-hydroxy-γ-lactone as the nucleophile, to form branched linear ethers, and an olefin ring-closing metathesis to obtain the oxepene core.
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expedient synthesis of c3 symmetric hexasubstituted benzenes via Nicholas Reaction 2 2 2 cycloaddition new platforms for molecular recognition
Organic Letters, 2014Co-Authors: Romen Carrillo, Tomas Martin, Matias Lopezrodriguez, Fernando Pinacho R CrisostomoAbstract:An expedient methodology to synthesize macrocyclic compounds in one step based on the Nicholas Reaction is disclosed. The key step features two intermolecular Reactions followed by an intramolecular Reaction from the starting dicobalt hexacarbonyl–propargylic complex. The macrocycles obtained were modified through [2 + 2 + 2] cycloaddition, generating two new C3-symmetric hexasubstituted benzene structures suitable for molecular recognition purposes.
Víctor S. Martín - One of the best experts on this subject based on the ideXlab platform.
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intramolecular Nicholas Reaction enables the stereoselective synthesis of strained cyclooctynes
Molecules, 2021Co-Authors: Diego M Monzon, Miguel A. Ramirez, Víctor S. Martín, Tomas Martin, Juan Manuel Betancort, David Diaz DiazAbstract:Cyclic products can be obtained through the intramolecular version of the Nicholas Reaction, which requires having the nucleophile connected to the alkyne unit. Here, we report the synthesis of 1-oxa-3-cyclooctynes starting from commercially available (1R,3S)-camphoric acid. The strategy is based on the initial preparation of propargylic alcohols, complexation of the triple bond with Co2(CO)8, and treatment with BF3·Et2O to induce an intramolecular Nicholas Reaction with the free hydroxyl group as nucleophile. Finally, oxidative deprotection of the alkyne afforded the cyclooctynes in good yields. Notably, large-sized R substituents at the chiral center connected to the O atom were oriented in such a way that steric interactions were minimized in the cyclization, allowing the formation of cyclooctynes exclusively with (R) configuration, in good agreement with theoretical predictions. Moreover, preliminary studies demonstrated that these cyclooctynes were reactive in the presence of azides yielding substituted triazoles.
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β hydroxy γ lactones as nucleophiles in the Nicholas Reaction for the synthesis of oxepene rings enantioselective formal synthesis of isolaurepinnacin i and rogioloxepane a ii
ChemInform, 2014Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Nuria Ortega, Tomas MartinAbstract:The key steps consist of an intermolecular Nicholas Reaction with a β-hydroxy-γ-lactone as a nucleophile and a ring closing metathesis Reaction.
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β hydroxy γ lactones as nucleophiles in the Nicholas Reaction for the synthesis of oxepene rings enantioselective formal synthesis of isolaurepinnacin and rogioloxepane a
Chemical Communications, 2014Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Tomas Martin, Nuria OrtegaAbstract:The enantioselective formal synthesis of (−)-isolaurepinnacin and (+)-rogioloxepane A has been achieved. The key steps are an intermolecular Nicholas Reaction with a β-hydroxy-γ-lactone as the nucleophile, to form branched linear ethers, and an olefin ring-closing metathesis to obtain the oxepene core.
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strategies for the synthesis of cyclic ethers of marine natural products
Synlett, 2013Co-Authors: Juan I Padron, Tomas Martin, Víctor S. MartínAbstract:This account describes our studies on the synthesis of natural products that contain cyclic ethers in their structures. An overview of the main methodologies is presented and several total syntheses developed by the group are described. We also discuss new applications based on the use of Prins and Nicolas Reactions as key steps in the preparation of oxygenated heterocyclic compounds. 1 Introduction 1.1 Natural Sources and Biogenesis 2 Carbon–Oxygen Bond-Formation Approach 2.1 Intramolecular Opening of Epoxy Alcohols and Related Bromo Cyclizations 2.2 Intramolecular Hetero-Michael Reaction of Alkoxy γ-Benzoyloxy α,β-Unsaturated Esters 2.3 Intramolecular Nicholas Reaction 3 Ring-Closing Metathesis of Unsaturated Linear Ethers 4 Prins Cyclization Promoted by Iron(III) salts 4.1 General Strategy 4.2 Cyclization Using Alkynols and the Formation of Vinyl Halides 4.3 The Use of Trimethylsilyl and Electron-Withdrawing Substituents in the Synthesis of 2,6-Disubstituted Tetrahydropyrans 4.4 Catalytic Prins Cyclization 4.5 Synthesis of Oxepanes 5 Summary
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epoxide opening cascades triggered by a Nicholas Reaction total synthesis of teurilene
Angewandte Chemie, 2013Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Tomas Martin, Fernando Pinacho R Crisostomo, Matias Lopezrodriguez, Nuria OrtegaAbstract:The way in which nature approaches the synthesis of complex molecules is a great source of inspiration to organic chemists for planning a synthetic route to a natural product. In this context, cascade cyclizations are considered a valuable tool for obtaining molecular complexity in a straightforward manner. Focusing on polycyclic ethers, it is well accepted by the scientific community that these types of compounds originate from a cascade cyclization of a polyepoxide backbone, thus leading to structures such as the ones depicted in Figure 1. Therefore, epoxide-opening cascades have been
Nuria Ortega - One of the best experts on this subject based on the ideXlab platform.
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β hydroxy γ lactones as nucleophiles in the Nicholas Reaction for the synthesis of oxepene rings enantioselective formal synthesis of isolaurepinnacin i and rogioloxepane a ii
ChemInform, 2014Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Nuria Ortega, Tomas MartinAbstract:The key steps consist of an intermolecular Nicholas Reaction with a β-hydroxy-γ-lactone as a nucleophile and a ring closing metathesis Reaction.
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β hydroxy γ lactones as nucleophiles in the Nicholas Reaction for the synthesis of oxepene rings enantioselective formal synthesis of isolaurepinnacin and rogioloxepane a
Chemical Communications, 2014Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Tomas Martin, Nuria OrtegaAbstract:The enantioselective formal synthesis of (−)-isolaurepinnacin and (+)-rogioloxepane A has been achieved. The key steps are an intermolecular Nicholas Reaction with a β-hydroxy-γ-lactone as the nucleophile, to form branched linear ethers, and an olefin ring-closing metathesis to obtain the oxepene core.
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epoxide opening cascades triggered by a Nicholas Reaction total synthesis of teurilene
Angewandte Chemie, 2013Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Tomas Martin, Fernando Pinacho R Crisostomo, Matias Lopezrodriguez, Nuria OrtegaAbstract:The way in which nature approaches the synthesis of complex molecules is a great source of inspiration to organic chemists for planning a synthetic route to a natural product. In this context, cascade cyclizations are considered a valuable tool for obtaining molecular complexity in a straightforward manner. Focusing on polycyclic ethers, it is well accepted by the scientific community that these types of compounds originate from a cascade cyclization of a polyepoxide backbone, thus leading to structures such as the ones depicted in Figure 1. Therefore, epoxide-opening cascades have been
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synthesis of α α disubstituted linear ethers by an intermolecular Nicholas Reaction application to the synthesis of cis trans lauthisan and cis trans obtusan
European Journal of Organic Chemistry, 2009Co-Authors: Nuria Ortega, Tomas Martin, Víctor S. MartínAbstract:A new and efficient methodology to prepare α,α′-disubstituted linear ethers through an intermolecular Nicholas Reaction (interNR) is described. cis-2,8-Disubstituted oxocanes, cis-2,9-disubstituted oxonanes, their trans isomers, and their parent unsaturated precursors were prepared from the corresponding Co2(CO)6–cycloalkynic ethers. Key steps in such syntheses were the ether linkage formation by interNR, RCM of the suitable acyclic dienyl ether, and montmorillonite K-10 induced isomerization of the complexed cycloalkyne. By taking advantage of the developed methodology a short synthesis of (+)-cis- and (–)-trans-lauthisan and (+)-cis- and (+)-trans-obtusan are described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
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stereoselective synthesis of eight membered cyclic ethers by tandem Nicholas Reaction ring closing metathesis a short synthesis of cis lauthisan
Organic Letters, 2006Co-Authors: Nuria Ortega, Tomas Martin, Víctor S. MartínAbstract:Cis-2,8-disubstituted oxocanes and the parent unsaturated precursors were prepared from the corresponding Co2(CO)6-cycloalkynic ethers. Key steps in such synthesis were the ether linkage formation by intermolecular Nicholas Reaction, RCM of the suitable acyclic dienyl ether and montmorillonite K-10 induced isomerization of the complexed cycloalkyne. A short synthesis of (+)-cis-lauthisan taking advantage of the developed methodology is described.
Fernando Pinacho R Crisostomo - One of the best experts on this subject based on the ideXlab platform.
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expedient synthesis of c3 symmetric hexasubstituted benzenes via Nicholas Reaction 2 2 2 cycloaddition new platforms for molecular recognition
ChemInform, 2014Co-Authors: Romen Carrillo, Tomas Martin, Matias Lopezrodriguez, Fernando Pinacho R CrisostomoAbstract:The new method is based on the Nicholas Reaction giving dimer (II) and macrocycle (III) which is further converted into the target compound by decomplexation and [2 + 2 + 2] cycloaddition under microwave irradiation.
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expedient synthesis of c3 symmetric hexasubstituted benzenes via Nicholas Reaction 2 2 2 cycloaddition new platforms for molecular recognition
Organic Letters, 2014Co-Authors: Romen Carrillo, Tomas Martin, Matias Lopezrodriguez, Fernando Pinacho R CrisostomoAbstract:An expedient methodology to synthesize macrocyclic compounds in one step based on the Nicholas Reaction is disclosed. The key step features two intermolecular Reactions followed by an intramolecular Reaction from the starting dicobalt hexacarbonyl–propargylic complex. The macrocycles obtained were modified through [2 + 2 + 2] cycloaddition, generating two new C3-symmetric hexasubstituted benzene structures suitable for molecular recognition purposes.
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epoxide opening cascades triggered by a Nicholas Reaction total synthesis of teurilene
Angewandte Chemie, 2013Co-Authors: Julio Rodriguezlopez, Víctor S. Martín, Tomas Martin, Fernando Pinacho R Crisostomo, Matias Lopezrodriguez, Nuria OrtegaAbstract:The way in which nature approaches the synthesis of complex molecules is a great source of inspiration to organic chemists for planning a synthetic route to a natural product. In this context, cascade cyclizations are considered a valuable tool for obtaining molecular complexity in a straightforward manner. Focusing on polycyclic ethers, it is well accepted by the scientific community that these types of compounds originate from a cascade cyclization of a polyepoxide backbone, thus leading to structures such as the ones depicted in Figure 1. Therefore, epoxide-opening cascades have been
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montmorillonite k 10 as a mild acid for the Nicholas Reaction
Tetrahedron Letters, 2005Co-Authors: Fernando Pinacho R Crisostomo, Tomas Martin, Romen Carrillo, Víctor S. MartínAbstract:Abstract The use of Montmorillonite K-10 as a convenient acid component in the Nicholas Reaction is described. Its use permits functional selectivity, inter- and intramolecular Reactions and convenience in the experimental conditions. A four-step one-pot [Co 2 (CO) 6 –acetylene complex formation, THP-removal, cyclization and complex cleavage] process permits the direct synthesis of 2-ethynyl-tetrahydrofuran from 6-(tetrahydro-2 H -pyran-2-yloxy)hex-1-yn-3-ol.
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stereoselective intramolecular Nicholas Reaction using epoxides as nucleophiles
Organic Letters, 2004Co-Authors: Fernando Pinacho R Crisostomo, Tomas Martin, Víctor S. MartínAbstract:The intramolecular nucleophilic attack of the epoxides on the exo-Co2(CO)6-propargylic cations provided cyclic ethers in good yields. The use of substrates with stereochemically defined oxiranes provided polysubstituted tetrahydropyrans and oxepanes with a high degree of stereocontrol. The cyclization is sensitive to the nature of the protecting group used at the primary alcohol, the use of tert-butyl carbonates being highly effective in terms of regioselectivity and yields.
James R. Green - One of the best experts on this subject based on the ideXlab platform.
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extension of the 5 alkynyluridine side chain via c c bond formation in modified organometallic nucleosides using the Nicholas Reaction
Beilstein Journal of Organic Chemistry, 2020Co-Authors: Renata Kaczmarek, James R. Green, Dariusz Korczynski, Roman DembinskiAbstract:Dicobalt hexacarbonyl nucleoside complexes of propargyl ether or esters of 5-substituted uridines react with diverse C-nucleophiles. Synthetic outcomes confirmed that the Nicholas Reaction can be carried out in a nucleoside presence, leading to a divergent synthesis of novel metallo-nucleosides enriched with alkene, arene, arylketo, and heterocyclic functions, in the deoxy and ribo series.
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Chemistry of Propargyldicobalt Cations: Recent Developments in the Nicholas and Related Reactions
2015Co-Authors: James R. GreenAbstract:Abstract: The chemistry of propargyldicobalt cations, also known as the Nicholas Reaction, is reviewed, with a focus on the developments since 1995. Advances in the understanding of the fundamental properties, such as structure, stability, and reactivity, of both the hexacarbonyl complexes and those bearing other ligands are discussed. All Reactions involving propargyl cation dicobalt complexes are covered, including those stemming from ionization of propargylic leaving groups and those created by electrophilic addition to enyne complexes. Migration Reactions involving either initiation or termination by propargyl cation complexes are included, as are the generation and Reactions of propargyldicobalt radicals. Cyclization Reactions employing these cations have received much attention, in cases with the alkynedicobalt unit located in both exocyclic and endocyclic positions, and these reports are described. Particular attention is paid to preparation of medium ring cycloalkyne complexes and their heterocyclic analogues. In addition, there is discussion of the progress in the in selectivity of these Reactions, especially in terms of introduction of asymmetry at the propargylic site. Finally, recent applications of Nicholas Reaction chemistry in the synthesis of natural products and related compounds are reported. INTRODUCTION The attention paid to these compounds is understandable. The cations (1) may be generated fro
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Synthesis of Tenuifolin through Intramolecular Nicholas Reaction
Synlett, 2014Co-Authors: Sinisa Djurdjevic, James R. GreenAbstract:The synthesis of the Cinnamomum homosesquiterpenoid tenuifolin (I) has been accomplished by way of an intramol. Nicholas Reaction of the [Co2(CO)6] complex of an alkyne-substituted biaryl for construction of the seven-membered ring. The cyclization features the Reaction of a nonactivated arene ring with the propargyl dicobalt cation to give the dibenzocycloheptyne-Co2(CO)6. [on SciFinder(R)]
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the synthesis of velloziolide via Nicholas Reaction based γ carbonyl cations
Journal of Organic Chemistry, 2009Co-Authors: James R. Green, Andy A TjengAbstract:The total synthesis of the 9,11-seco-rosane diterpene velloziolide (1) has been accomplished by employing the Nicholas Reaction chemistry of 2a as a γ-carbonyl cation equivalent. An initial model s...
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cyclohepta de naphthalenes and the rearrangedabietane framework of microstegiol via Nicholas Reaction chemistry
Synlett, 2009Co-Authors: Rafiq A Taj, Anusha Abhayawardhana, James R. GreenAbstract:Nicholas Reactions on 2,7-dioxygenated naphthalenes give C-1monosubstitution and C-1/C-8 disubstitution in most -cases.From γ-carbonyl cation monocondensation product 3B or alkyne-unsubstituted dicondensationproduct 4A, cyclohepta[ DE]naphthalenes bearing no substituents, GEM-dimethyl substituents, and a ketonefunction, and the rearranged abietane framework of microstegiolmay be prepared.