Recent Advances in Transition-Metal-Catalyzed Iodination of Arenes

Sloan, Nikki L.; Sutherland, Andrew

doi:10.1055/s-0035-1562439

Cited by 22 publications

(4 citation statements)

References 59 publications

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“…36 However, the site-selective installation of multiple halogen sites (e.g., via sequential fluorination and iodination) remained an unsolved challenge, in particular because of the incompatibilities of reactive handles toward reaction conditions and the low selectivities in different halogenation strategies. 4,37 Intrigued by the robustness of ArGeEt 3 on the one hand and the high reactivity in electrophilic approaches on the other, 1 we started to investigate halonium sources (electrophilic halogen sources) in ipso-halogenation with ArGeEt 3 to eventually target multihalogenation of molecules. 4 Established halogenation strategies of other nucleophilic sites (C−[B], C−[Sn], and C−[Si]) displayed either lower reactivity in direct halogenation (e.g., ArBpin or ArSiMe 3 ) or less practical handling of reagents (e.g., ArB(OH) 2 ).…”

Section: Ipso-halogenation Of Argeetmentioning

confidence: 99%

Organogermanes as Orthogonal Coupling Partners in Synthesis and Catalysis

2020

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Conspectus Since the advent of metal-catalyzed cross-coupling technology more than 40 years ago, the field has grown to be ever-increasingly enabling, yet the employed coupling partners are largely still those that were originally employed in the context of Pd-catalyzed cross-coupling, namely, arylboronic esters/acids, aryl silanes, aryl stannanes, or organometallic reagents (RMgX, RZnX). Aryl germanes have little precedent in the literature; they were historically explored in the context of Pd0/PdII-catalyzed cross-coupling reactions but were found to be much less reactive than the already established reagents. Consequently, few efforts were made by the community on their further mechanistic or synthetic exploration. In 2019, our group described trialkyl aryl germanes as robust, convenient, and nontoxic reagents. Although structurally similar to trialkyl aryl stannanes or silanes, the GeEt3 site does not engage in the traditional transmetalation mode of PdII complexes. Our studies instead provided strong support for an unprecedented and orthogonal reactivity of organogermanes that follows electrophilic aromatic substitution (SEAr)-type reactivity. This mode of bond activation allowed us to devise a number of synthetic strategies in which the Ge functionality was for the first time more reactive and exclusively functionalized in preference over several of the established coupling partners (e.g., silanes, boronic acids/esters, halogens). Within the past year we have showcased the unique reactivity of organogermanes in C–C and C–X bond-forming transformations. Because of the exquisite mode of bond activation, the new strategies offer access to complementary chemical transformations, tolerating other cross-coupling enabling functionalities, and allow for their further downstream diversification. We have for instance demonstrated that organogermanes can be coupled efficiently with aryl halides under Pd nanoparticle conditions with tolerance of all other established cross-coupling partners, while under homogeneous Pd0/PdII catalysis all of the other established groups can be functionalized preferentially over the Ge functionality. We similarly were able to harness this orthogonal reactivity mode in oxidative gold catalysis, where organogermanes proved to be more reactive than the established silanes or boronic esters. We have also developed an orthogonal approach for metal-free halogenation of organogermanes with convenient halogenation agents, offering access to the chemo- and regioselective installation of valuable halide motifs in the presence of alternative groups that can also engage in electrophilic halogenations. In this Account, we wish to provide an overview of (i) the historic versus current reactivity findings and synthetic utility of organogermanes, (ii) the current state of mechanistic understanding of their reactivity, and (iii) the synthetic repertoire and ease of installing the germanium functionality in organic molecules.

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Section: Ipso-halogenation Of Argeetmentioning

confidence: 99%

Organogermanes as Orthogonal Coupling Partners in Synthesis and Catalysis

2020

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“…3 The halogenation of suitable precursor functionalities, such as aryl metals, provides an alternative method for synthesizing aryl halides (Scheme 1a). 4 However, traditional halogenation still requires stoichiometric hazardous oxidants, expensive metal catalysts, toxic halogenating reagents, or strongly alkaline reaction media, which may cause environmental and safety problems. Meanwhile, a strongly oxidizing or alkaline reaction system might lead to low selectivity and inefficiency.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical (radio)-halodesilylation of aromatic silanes

Gong,

Lin,

Gao

et al. 2024

Org. Chem. Front.

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“…1A(I) ). 3 However, the iodination of structurally complex arenes remains more challenging than the analogous chlorination and bromination, due to the limited availability of suitable electrophilic iodinating reagents, the typically required harsh reaction conditions leading to poor functional group tolerance. 4 Recent research has aimed for milder and more efficient electrophilic C–H iodination enabling the functionalization of challenging and complex molecules.…”

Section: Introductionmentioning

confidence: 99%