Ni‐Catalyzed Stannylation of Aryl Esters via C−O Bond Cleavage

Gu, Yiting; Martı́n, Rubén

doi:10.1002/ange.201611720

Cited by 14 publications

(1 citation statement)

References 71 publications

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“…4a). Importantly, similar transformations in the field of C−O bond activation were previously reported in the presence of an exogenous base 41,[43][44][45][46] .…”

Section: Niesupporting

confidence: 75%

Non-Innocent Electrophiles Unlock Exogenous Base-Free Coupling Reactions

Toupalas¹,

Morandi

2021

Preprint

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Transition metal catalysis has revolutionized our ability to precisely manipulate matter and has placed itself at the forefront of the combat against societal challenges through key discoveries in drug design, agriculture, material synthesis and environmental sciences. Numerous important transition metal catalyzed reactions rely on stoichiometric quantities of an exogenous base to enable catalytic turnover. Despite playing a fundamental role, paradoxically, the base poses major challenges on several fronts, such as restricting the accessible chemical space due to functional group incompatibilities, or causing heterogeneous reaction mixtures that affect reproducibility, scale-up campaigns, and the implementation of emerging technologies, e.g. flow chemistry or high-throughput experimentation. Ultimately, this impedes innovation across multiple areas. Here we introduce a unifying strategy that eliminates the need for an exogenous base through the use of non-innocent electrophiles (NIE). Key to its success was the encryption of the base into the electrophile rendering it non-innocent, thus preserving the synthetic utility of the original reaction while overcoming the challenges associated with the exogenous base. The use of nickel as an earth-abundant metal catalyst as well as the employment of ubiquitous phenol derivatives as non-innocent electrophiles are further salient features of this sustainable protocol. The universal applicability of this concept was demonstrated by turning multiple traditionally base-dependent catalytic reactions, e.g. the Buchwald-Hartwig amination, the Mizoroki-Heck reaction and the Suzuki-Miyaura coupling, into exogenous base-free homogeneous processes. In a broader context, the results presented in this work provide a conceptual blueprint for the utilization of non-innocent electrophiles to overcome core limitations and unlock novel features in catalysis.

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“…4a). Importantly, similar transformations in the field of C−O bond activation were previously reported in the presence of an exogenous base 41,[43][44][45][46] .…”

Section: Niesupporting

confidence: 75%

Non-Innocent Electrophiles Unlock Exogenous Base-Free Coupling Reactions

Toupalas¹,

Morandi

2021

Preprint

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Synthesis of Arylstannanes via Palladium‐Catalyzed Decarbonylative Coupling of Aroyl Fluorides

et al. 2019

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Aryl stannanes are valuable precursors in organic transformations, but their synthetic methods are limited. Here we present a Pd‐catalyzed decarbonylative stannylation of acid fluorides in the absence of exogenous base. Various aryl stannanes were efficiently prepared from bench‐stable transition metal catalyst and ligand with broad functional group compatibility and substrate scope including natural products and pharmaceuticals. This protocol was also successfully used to a late‐stage diversification of an existing uricosuric drug probenecid.

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Efficient Aryl Migration from an Aryl Ether to a Carboxylic Acid Group To Form an Ester by Visible‐Light Photoredox Catalysis

Wang

Cao

2017

Angewandte Chemie

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We have developed ahighly efficient aryl migration from an aryl ether to ac arboxylic acid group through retro-Smiles rearrangement by visible-light photoredoxc atalysis at ambient temperature.T ransition metals and as toichiometric oxidant and base are avoided in the transformation. Inspired by the high efficiency of this transformation and the fundamental importance of C À Ob ond cleavage,w ed eveloped anovel approachtothe C À Ocleavage of abiaryl ether to form two phenolic compounds,a sd emonstrated by ao ne-pot, twostep gram-scale reaction under mild conditions.T he aryl migration exhibits broad scope and can be applied to the synthesis of pharmaceutical compounds,s uch as guacetisal. Primary mechanistic studies indicate that the catalytic cycle occurs by ar eductive quenchingpathway.Various aryl-migration reactions have been developed and display broad application. [1] Notably,a ryl migration from an aryl ether to form an ester is rare.In1955, this migration was first observed upon the thermal decomposition of 2-phenoxybenzoyl peroxide in 25 %y ield by DeTar and Hlynsky. [2] Recently,t he migration was promoted by silver catalysis at 130 8 8CbyHossian and Jana, who used acarboxylic acid as the starting material. [3] However,t he stoichiometric strong oxidant K 2 S 2 O 8 and ab ase were required. Furthermore,t he transformation only resulted in up to 64 %y ield. No clear electronic effects on this aryl migration were observed. Thus, the transformation was identified as aSmiles rearrangement. Herein, we demonstrate ahighly efficient aryl migration from an aryl ether to form the ester of acarboxylic acid by visiblelight photoredox catalysis at ambient temperature without an oxidant [Scheme 1, Eq. (1)].O nly 1mol %o faphotosensitizer (PDI or Acr + -Mes ClO 4 À )a nd 10 mol %o fabase (K 2 HPO 4 )w ere required. Notably,e lectron-donating groups on the migrating aryl ring generally induced higher yields in this transformation, which differs from the typical Smiles rearrangement [4] and can be understood as ar etro-Smiles rearrangement. [4a,5] As this developed aryl migration is the retro-reaction of the reported Smiles rearrangement involving aryl migration from an ester to form an aryl ether. [6] And the Smiles rearrangement always requires ah eteroatom as the nucleophilic component and an electrophilic arene activated by strong electron-withdrawing groups,acarbonbased nucleophile,orfree-radical attack on the ipso-position of sulfonates or sulfonamides. [4] By taking advantage of visible-light photoredox catalysis,transition metals and astoichiometric amount of an oxidant and abase are avoided, thus leading to an environmentally benign and highly atom economical transformation. Moreover,i nspired by the high efficiency of this aryl migration and the fundamental importance of CÀOb ond cleavage, [4i, 7] we demonstrate an ovel approach to CÀOb ond cleavage in biaryl ethers to give two phenolic compounds in ao ne-pot, two-step reaction under mild conditions as as ubsequent transformation [Scheme 1, Eq. (2)].Visible...

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Ni‐Catalyzed Stannylation of Aryl Esters via C−O Bond Cleavage

Cited by 14 publications

References 71 publications

Non-Innocent Electrophiles Unlock Exogenous Base-Free Coupling Reactions

Non-Innocent Electrophiles Unlock Exogenous Base-Free Coupling Reactions

Synthesis of Arylstannanes via Palladium‐Catalyzed Decarbonylative Coupling of Aroyl Fluorides

Efficient Aryl Migration from an Aryl Ether to a Carboxylic Acid Group To Form an Ester by Visible‐Light Photoredox Catalysis

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