Palladium(II)-Catalyzed C–H Bond Activation/C–C and C–O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans

Neog, Kashmiri; Borah, Ashwini; Gogoi, Pranjal

doi:10.1021/acs.joc.6b01966

Cited by 68 publications

(22 citation statements)

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“…A promising approach to construct these structures is the oxidative coupling between the catechols and hydroxycoumarins . This reaction has two advantages over other reactions that use halogen‐, trifluoromethanesulfonate‐ or tributyltin‐substituted aromatic compounds as the starting material. This method allows the direct use of substrates without prefunctionalization and involves the formation of C−C and C−O bonds in a cascade‐type reaction.…”

Section: Figurementioning

confidence: 99%

Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O₂ as an Oxidant Catalyzed by AlPO₄‐Supported Rh Nanoparticle

et al. 2019

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An efficient synthesis of benzofuran derivatives via the cross‐coupling of catechols and hydroxycoumarins in H2O using O2 as an ideal oxidant is reported. The above reaction allows the direct use of substrates without prefunctionalization, involves formation of C−C and C−O bonds in cascade manner, and affords H2O as the sole by‐product. This simple and clean reaction is achieved by the development of an AlPO4‐supported Rh nanoparticle catalyst. The catalyst was applicable to the synthesis of a wide range of benzofurans. We also successfully utilized this catalytic method for total synthesis of flemichapparin C, one of the naturally occurring coumestans exhibiting bioactivity. The combined functions of Rh nanoparticles and AlPO4 play a key role in this reaction where in situ generated o‐benzoquinone by Rh nanoparticles is possibly an intermediate for nucleophilic addition to hydroxycoumarins on AlPO4.

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Section: Figurementioning

confidence: 99%

Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O₂ as an Oxidant Catalyzed by AlPO₄‐Supported Rh Nanoparticle

et al. 2019

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“…Gogoi and co‐workers reported the direct synthesis of coumestans via a palladium‐catalysed C–H activation/C–C and C–O bond formation cascade invoking aryne chemistry (Scheme ) . Flemichapparin C was also synthesised using this methodology.…”

Section: C–h Activation Of 2‐coumarinsmentioning

confidence: 99%

Transition Metal Mediated C–H Activation of 2‐Pyrones, 2‐Pyridones, 2‐Coumarins and 2‐Quinolones

Prendergast

McGlacken

2018

Eur J Org Chem

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C–H activation has emerged as a viable alternative to traditional C–C bond forming reactions such as the Suzuki–Miyaura, Stille, Negishi and others. However, C–H activation is rarely employed in total synthesis or fine chemical manufacture, particularly as an end‐game strategy. This may be due to the harsh conditions typically required. For C–H activation to become a truly useful and versatile methodology, conditions must emerge which are applicable to compounds with multiple functionalities. In this review, we hope to inspire the chemistry community to focus their efforts on milder conditions for C–H activation and cross‐dehydrogenative coupling. To this end, we have focused on describing C–H activation as it has been applied to several classes of biologically interesting, but chemically sensitive motifs: the 2‐pyrones, 2‐pyridones, 2‐coumarins and 2‐quinolones.

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“…In 2016, Gogoi et al reported the synthesiso fc oumestans 447 from 4-hydroxycoumarins 446 and benzyne precursors 223 (Scheme 129). [185] Thea uthors propose C(sp 2 )-H activation assisted by the coordina- tion of Pd(II) to the alcohol for the formation of coumaroyl-Pd(II) complex 448.I nsertiono ft he benzyne formsintermediate 449 andaBuchwald-Hartwig-type etherification forms the product.B road variation of the R 1 substitution is tolerated, providing the coumestans in good yields.N or egioselectivity was obtained when the benzyne was unsymmetrically substituted.…”

Section: C-h Activationmentioning

confidence: 99%

Advances in Palladium‐Catalyzed Cascade Cyclizations

Biemolt

Ruijter

2018

Adv Synth Catal

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Thep ast decades in organic chemistry have witnessed significant improvements in synthetic efficiency as ar esult of considerable progress in cascade reactions,t andem reactions,a nd related onepot processes. These methods are less time-consuming andp roduce less waste comparedt ot he classical stepwise approach. However, cascade chemistry requires am ore careful design and compatible reaction types for success.P alladium-catalyzed cross-coupling reactions,w ith their well understoodm ultistep catalytic cycles,f orm ap romising basis for the design of cascade reactions.F urthermore,t hey are compatible with ar ange of functional groups and can be combined with ar ange of secondary transformations. Ther esulting palladium-catalyzed cascade reactions have provided access to ap lethorao fc omplex small molecules of high medicinal relevance.T his review providesa no verview of the developments in palladium-catalyzed cascade reactions since 2011, classified according to the initiation, propagation, andtermination steps comprising the palladium cascade reactions.T hisc lassification should assist the reader and may provide inspiration for the design of newc ascade reactions.

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Palladium(II)-Catalyzed C–H Bond Activation/C–C and C–O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans

Cited by 68 publications

References 50 publications

Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O₂ as an Oxidant Catalyzed by AlPO₄‐Supported Rh Nanoparticle

Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O₂ as an Oxidant Catalyzed by AlPO₄‐Supported Rh Nanoparticle

Transition Metal Mediated C–H Activation of 2‐Pyrones, 2‐Pyridones, 2‐Coumarins and 2‐Quinolones

Advances in Palladium‐Catalyzed Cascade Cyclizations

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Palladium(II)-Catalyzed C–H Bond Activation/C–C and C–O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans

Cited by 68 publications

References 50 publications

Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O2 as an Oxidant Catalyzed by AlPO4‐Supported Rh Nanoparticle

Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O2 as an Oxidant Catalyzed by AlPO4‐Supported Rh Nanoparticle

Transition Metal Mediated C–H Activation of 2‐Pyrones, 2‐Pyridones, 2‐Coumarins and 2‐Quinolones

Advances in Palladium‐Catalyzed Cascade Cyclizations

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Product

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Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O₂ as an Oxidant Catalyzed by AlPO₄‐Supported Rh Nanoparticle

Efficient Synthesis of Benzofurans via Cross‐Coupling of Catechols with Hydroxycoumarins Using O₂ as an Oxidant Catalyzed by AlPO₄‐Supported Rh Nanoparticle