Iridium(III)-Catalyzed Regioselective B(4)–H Allenylation of <i>o</i>-Carboranes by Ball Milling

Shin, Seohyun; Um, Kyusik; Ko, Gi Hoon; Han, Gi Uk; Kim, Dongwook; Lee, Phil Ho

doi:10.1021/acs.orglett.2c00756

Cited by 15 publications

(5 citation statements)

References 57 publications

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“…Utilizing ball milling strategy, the Lee group achieved an Ir-catalyzed cage B(4)-H allenylation of carboranyl carboxylic acids 1 with propargyl carbonates to afford a class of B(4)-allenylated o-carboranes 42 in good to excellent yields (Scheme 10); 27 this could hardly be achieved under conventional solution-based conditions. A range of functional substituents, including halo, methoxy, ester, nitro, (benzo)thiophenyl, and benzofuranyl groups, were compatible with the reaction.…”

Section: Review Synthesismentioning

confidence: 99%

Directing-Group-Assisted Transition-Metal-Catalyzed Selective BH Functionalization of o-Carboranes

Xie,

Zhang

2024

Synthesis

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Carboranes are a type of molecular clusters consisting of carbon, hydrogen and boron atoms. They possess unique characteristics such as three-dimensional aromaticity, icosahedral geometry, and robustness. Functionalized carboranes have been utilized in various fields including medicine, materials, and organometallic/coordination chemistry. In this context, selective functionalization of o-carboranes has received tremendous attention, specifically in the regio- and enantio-selective modification of the ten chemically similar BH vertices within the carborane cage. In recent years, significant progress has been made in catalytic vertex-specific BH functionalization, as well as achieving enantioselective functionalization of the cage BH. This review provides an overview of the recent advancements in this research field.

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Section: Review Synthesismentioning

confidence: 99%

Directing-Group-Assisted Transition-Metal-Catalyzed Selective BH Functionalization of o-Carboranes

Xie,

Zhang

2024

Synthesis

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“…Stimulated by aforementioned reaction and previously reported C(1)À H and B(3)À H allenylation, an allenyl group was introduced into B(4) vertex of ocarborane via BÀ H activation was reported by Lee's group reported very recently (Scheme 10). [22] A variety of previously inaccessible B(4)-allenylated o-carboranes were readily synthesized under the ball milling [CB 11 H 12 ] À also is a kind of icosahedral cage compounds that can be derivatized. Although the progress made in o-carboranes are well known, transition metal-catalyzed BÀ H functionalization of anionic boron clusters is less much studied.…”

Section: Scheme 6 Ir-catalyzed Selective Dehydrogenative Cross Coupli...mentioning

confidence: 99%

Recent Advance in Transition Metal‐Catalyzed Carboxylic Acid Guided B−H Functionalization of Carboranes

et al. 2022

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Carboranes, a three-dimensional class of carbon-boron molecular clusters with remarkable electronic, physical, chemical characteristics, have proved as useful building blocks in boron neutron capture therapy agents, supramolecular design, optoelectronics, nanomaterials and organometallic/coordination chemistry. Thus, various organic modifications of the BÀ H and CÀ H functionalities in carboranes have been developed. These methods with great success utilize directing groups, such as carboxylic acids, to achieve a selective BÀ H functionalization of carboranes. The carboxyl group can be easily introduced to carboranes and then be removed after reactions. On the other hand, assisted by the carboxyl group a highly regioselective electrophilic attack at the electron-rich positions B(4) and B(5) of the cage generates five-membered metallacyclic intermediates, which then undergo further transformation. In this review, we show that transition metal-catalyzed decarboxylation cross coupling reactions offer an opportunity for the selective and direct BÀ H activation of carboranes. 1. Introduction 2. Formation of BÀ C(sp 2 ) Bonds 3. Formation of BÀ C(sp) Bonds 4. Formation of BÀ C(sp 3 ) Bonds 5. Formation of BÀ N Bonds 6. Formation of BÀ O Bonds 7. Formation of BÀ X Bonds 8. Formation of BÀ N Bonds and BÀ C(sp 2 ) Bonds 9. Formation of CÀ N Bonds 10. Conclusions and Outlooks

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“…It is also essential to control the regioselectivity because the substitution at B(8/10) and B(9) positions generates corresponding regioisomers. In our continuing efforts to develop e cient and regioselective B − H functionalization of o-carboranes [44][45][46][47][48][49][50][51][52][53][54][55][56][57] , we demonstrate herein the iridium(III)-catalyzed templateassisted remote B(9) − H alkylation reaction of o-carboranes (e). This unprecedented alkylation reaction of readily accessible o-carboranes possessing nitrile template shows high regioselectivity.…”

Section: Introductionmentioning

confidence: 99%

Iridium(III)-catalyzed remote B(9)−H alkylation of o-carboranes with nitrile template

Lee,

Kim

et al. 2024

Preprint

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Although the directing group assisted ortho-B − H activation reactions of o-carboranes have been well established during the past decade, the meta-B − H activation reactions are unexplored so far. Herein, iridium(III)-catalyzed remote B(9) − H alkylation reactions of o-carboranes with nitrile template have been demonstrated for the first time. It was revealed that fine tuning of the template structures is essential for high reaction efficiency and regioselectivity. This alkylation process exhibits a broad substrate scope with good functional group tolerance under simple reaction conditions. The nitrile template, readily accessible from o-carborane acids, can be removed conveniently after completion of the reaction. The present method provides a powerful synthetic route to complex o-carborane derivatives, demonstrating successful larger scale alkylation and further molecular transformations of the B(9)-alkylated products.

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Iridium(III)-Catalyzed Regioselective B(4)–H Allenylation of o-Carboranes by Ball Milling

Cited by 15 publications

References 57 publications

Directing-Group-Assisted Transition-Metal-Catalyzed Selective BH Functionalization of o-Carboranes

Directing-Group-Assisted Transition-Metal-Catalyzed Selective BH Functionalization of o-Carboranes

Recent Advance in Transition Metal‐Catalyzed Carboxylic Acid Guided B−H Functionalization of Carboranes

Iridium(III)-catalyzed remote B(9)−H alkylation of o-carboranes with nitrile template

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