Highly selective electrophilic B(9)-amination of <i>o</i>-carborane driven by HOTf and HFIP

Wang, Yan; Gao, Yan; Guo, Wenjing; Zhao, Qianyi; Ma, Yan‐Na; Chen, Xuenian

doi:10.1039/d2qo00732k

Cited by 16 publications

(12 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Based on our previous work on the electrophilic substitution reactions of o -carboranes in HFIP, , we conducted the reaction of o -carborane and 68% HNO 3 in HFIP (Table , entry 1). Unfortunately, initial attempts did not deliver any product.…”

Section: Resultsmentioning

confidence: 99%

B(9)-OH-o-Carboranes: Synthesis, Mechanism, and Property Exploration

Ren

et al. 2023

J. Am. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

Herein, we present a chemically robust and efficient synthesis route for B(9)-OH-o-carboranes by the oxidation of ocarboranes with commercially available 68% HNO 3 under the assistance of trifluoromethanesulfonic acid (HOTf) and hexafluoroisopropanol (HFIP). The reaction is highly efficient with a wide scope of carboranes, and the selectivity of B(9)/B(8) is up to 98:2. The success of this transformation relies on the strong electrophilicity and oxidizability of HNO 3 , promoted through hydrogen bonds of the Brønsted acid HOTf and the solvent HFIP. Mechanism studies reveal that the oxidation of o-carborane involves an initial electrophilic attack of HNO 3 to the hydrogen atom at the most electronegative B(9) of o-carborane. In this transformation, the hydrogen atom of the B−H bond is the nucleophilic site, which is different from the electrophilic substitution reaction, where the boron atom is the nucleophilic site. Therefore, this is an oxidation−reduction reaction of o-carborane under mild conditions in which N(V) → N(III) and H(-I) → H(I). The derivatization of 9-OH-o-carborane was further examined, and the carboranyl group was successfully introduced to an amino acid, polyethylene glycol, biotin, deoxyuridine, and saccharide. Undoubtedly, this approach provides a selective way for the rapid incorporation of carborane moieties into small molecules for application in boron neutron capture therapy, which requires the targeted delivery of boron-rich groups.

show abstract

Section: Resultsmentioning

confidence: 99%

B(9)-OH-o-Carboranes: Synthesis, Mechanism, and Property Exploration

Ren

et al. 2023

J. Am. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Based on our previous reports, , we initially examined the influence of Brønsted acids on the electrophilic chlorination of o -carborane under one equivalent halogenating agent TCCA in HFIP solvent (Table , entries 1–4). It was found that the addition of Brønsted acids could slightly promote the reaction, and the best result was obtained when HOTf was used.…”

Section: Resultsmentioning

confidence: 99%

“…Based on our previous reports, 12,15 we initially examined the influence of Brønsted acids on the electrophilic chlorination of o-carborane under one equivalent halogenating agent TCCA in HFIP solvent (Table 1, entries 1−4 and the best result was obtained when HOTf was used. The yields of the desired product 9-Cl-o-carborane 1 increased significantly with the increase of HOTf (Table 1, entries 2, 5, and 6).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Very recently, we found that HOTf could promote the electrophilic amination of o-carboranes by forming a strong organocatalyst that acts as an excellent hydrogen bond donor to activate electrophiles. 15 With continuing interest in the selective B(9)-functionalization of o-carboranes in HFIP 16 and the great importance of the halogenated carboranes, we turned our attention to the HOTf-promoted electrophilic halogenation of o-carborane and m-carborane in HFIP. Through our endeavor, the monohalogenation and dihalogenation of ocarborane and m-carborane were rapidly realized using one and two equivalent halogenating agents at room temperature (Scheme 1b).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Under elevated temperatures or with long reaction time, monohalogenating carboranes were obtained. Very recently, we found that HOTf could promote the electrophilic amination of o -carboranes by forming a strong organocatalyst that acts as an excellent hydrogen bond donor to activate electrophiles . With continuing interest in the selective B(9)-functionalization of o -carboranes in HFIP and the great importance of the halogenated carboranes, we turned our attention to the HOTf-promoted electrophilic halogenation of o -carborane and m -carborane in HFIP.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Method for Highly Selective Halogenation of o-Carboranes and m-Carboranes

et al. 2022

Inorg. Chem.

Self Cite

View full text Add to dashboard Cite

A facile halogenation method for highly selective synthesis of 9-X-o-carboranes, 9,12-X2-o-carboranes, 9-X-12-X’-o-carboranes, 9-X-m-carboranes, 9,10-X2-m-carboranes, and 9-X-10-X’-m-carboranes (X, X’ = Cl, Br, I) has been developed on the basis of our previous work. The success of this transformation relies on the usage of trifluoromethanesulfonic acid (HOTf), the easily available strong Brønsted acid. The addition of HOTf greatly increases the electrophilicity of N-haloamides through hydrogen bonding interaction, resulting in the low loading of N-haloamides, short reaction time, and mild reaction conditions. Additionally, the solvent 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) is also essential to further increase the acidity of HOTf.

show abstract

Ruthenium‐Catalyzed Selective B(4)‐H Amidation of o‐Carboranes with Dioxazolones

2023

View full text Add to dashboard Cite

A ruthenium‐catalyzed selective B4 amidation of o‐carboranes with a variety of alkyl‐, aryl‐, and heteroaryl‐substituted dioxazolones is developed by carboxylic acid‐assisted B(4)‐H bond activation in o‐carborane acids, affording a multitude of (4)‐amidated o‐carboranes in good yields with the evolution of carbon dioxide. In addition, the two‐fold selective decarboxylative amidation reaction of the cage B(4)‐H bond in o‐carborane was accomplished.

show abstract

Highly selective electrophilic B(9)-amination of o-carborane driven by HOTf and HFIP

Abstract: Despite the great importance of nitrogen-containing carboranes in organic and pharmaceutical synthesis, current methods to generate them are very limited and usually rely on the use of expensive transition metals....

Cited by 16 publications

References 75 publications

B(9)-OH-o-Carboranes: Synthesis, Mechanism, and Property Exploration

B(9)-OH-o-Carboranes: Synthesis, Mechanism, and Property Exploration

A Method for Highly Selective Halogenation of o-Carboranes and m-Carboranes

Ruthenium‐Catalyzed Selective B(4)‐H Amidation of o‐Carboranes with Dioxazolones

Contact Info

Product

Resources

About