New Cascade Processes on Group 6 Fischer-Type Carbene Complexes:  Cyclopropanation and Metathesis Reactions

Barluenga, José; Andina, Facundo; Aznar, and Fernando; Valdés, Carlos

doi:10.1021/ol701604g

Cited by 35 publications

(12 citation statements)

References 25 publications

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“…These data are comparable with those reported in the literature for similar products obtained from Fisher carbene complexes. [31,32] However, in the literature procedures, alkenyl cyclobutenyl Fisher carbenes were first obtained by [2 + 2] cycloaddition between enol ethers (alkenylethynyl)carbene complexes. Thermal CO insertion and cyclization then led to o -methoxyphenol derivatives containing the fused BCB-cyclic ether core, through a process similar to the Dötz reaction.…”

Section: Resultsmentioning

confidence: 99%

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Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

et al. 2014

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Benzocyclobutenes (BCBs) are important entities in a multitude of areas, such as complex organic synthesis, materials and polymer chemistry, and electronics. Whereas reactions between arynes and ketene acetals have been well studied, reactions with cyclic enol ethers are unknown. A cis olefin geometry in cyclic enol ethers makes them well suited for formal [2 + 2] cycloaddition with arynes than for competing ene reactions, making them effective reactants. Reactions of 2,3-dihydrofuran, 2,3-dihydro-3H-pyran, 5-butyl-2,3-dihydrofuran, (S)-2-((benzyloxy)methyl)-2,3-dihydrofuran, and 1,4-dioxene with various arynes were successful. An advantage of the use of cyclic enol ethers is that despite the plausible intermediacy of zwitterionic intermediates, the products are limited to a cis ring junction. This can be exploited for potential access to stereochemically-defined 1,2-disubstituted BCBs. As a demonstration, ether ring cleavage with BBr3 provided trans-functionalized BCBs and displacement with azide then provided cis derivatives. DFT computations have been utilized to understand the structures of three arynes in relation to the cycloadditions and for a predictive evaluation of product ratios in two cases. A comparative evaluation of the HOMO energies of a related series of cyclic olefins has also been performed by DFT computations.

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Section: Resultsmentioning

confidence: 99%

“…[31] A similar approach has also been used for the synthesis of methoxy naphthalene derivatives by a metathesis pathway. [32] …”

Section: Resultsmentioning

confidence: 99%

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

et al. 2014

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“…With these results in hand, we further explored the substrate scope using the 1-ethynyl-2-vinylbenzene ( 4d ). 18 4d was reacted with ester 1a and the B(C 6 F 5 ) 3 /Mes 3 P FLP under the optimized reaction conditions (THF, 70 °C, 24 h). Contrary to the reactions above, the reactions were found to be highly site-selective for the C sp 3 –C sp 2 coupled product, 3 , from reaction at the alkene functional group.…”

Section: Results and Discussionmentioning

confidence: 99%

Site-Selective C_sp³–C_sp/C_sp³–C_sp² Cross-Coupling Reactions Using Frustrated Lewis Pairs

et al. 2021

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The donor–acceptor ability of frustrated Lewis pairs (FLPs) has led to widespread applications in organic synthesis. Single electron transfer from a donor Lewis base to an acceptor Lewis acid can generate a frustrated radical pair (FRP) depending on the substrate and energy required (thermal or photochemical) to promote an FLP into an FRP system. Herein, we report the C sp 3 –C sp cross-coupling reaction of aryl esters with terminal alkynes using the B(C 6 F 5 ) 3 /Mes 3 P FLP. Significantly, when the 1-ethynyl-4-vinylbenzene substrate was employed, the exclusive formation of C sp 3 –C sp cross-coupled products was observed. However, when 1-ethynyl-2-vinylbenzene was employed, solvent-dependent site-selective C sp 3 –C sp or C sp 3 –C sp 2 cross-coupling resulted. The nature of these reaction pathways and their selectivity has been investigated by extensive electron paramagnetic resonance (EPR) studies, kinetic studies, and density functional theory (DFT) calculations both to elucidate the mechanism of these coupling reactions and to explain the solvent-dependent site selectivity.

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“…1 and 2). 141 The which is formed by consecutive 8-and 6-electrocyclizations. This difference in reactivity between terminal and substituted olefins is attributed to the steric repulsion between the substituent in the olefin and the metal fragment, which disfavors the 8-electrocyclization.…”

Section: Scheme 48 Synthesis Of Phenanthrene Derivatives By Cycloaromentioning

confidence: 99%

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

et al. 2016

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ABSTRACT:1,3-Dien-5-ynes have been extensively used as starting materials for the synthesis of a wide number of different carbo-and heterocycles. The aim of this review is to give an overview of their utility in organic synthesis, highlighting the variety of compounds that can be directly accessed from single reactions over these systems. Thus, cycloaromatization processes are initially commented, followed by reactions directed towards the syntheses of five-membered rings, other carbocycles and, finally, heterocycles. The diverse methodologies that have been developed for the synthesis of each of these types of compounds from 1,3-dien-5-ynes are presented, emphasizing the influence of the reaction conditions and the use of additional reagents in the outcome of the transformations.2

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New Cascade Processes on Group 6 Fischer-Type Carbene Complexes: Cyclopropanation and Metathesis Reactions

Cited by 35 publications

References 25 publications

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Site-Selective C_sp³–C_sp/C_sp³–C_sp² Cross-Coupling Reactions Using Frustrated Lewis Pairs

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

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New Cascade Processes on Group 6 Fischer-Type Carbene Complexes: Cyclopropanation and Metathesis Reactions

Cited by 35 publications

References 25 publications

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Site-Selective Csp3–Csp/Csp3–Csp2 Cross-Coupling Reactions Using Frustrated Lewis Pairs

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

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Product

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Site-Selective C_sp³–C_sp/C_sp³–C_sp² Cross-Coupling Reactions Using Frustrated Lewis Pairs