Regioselective Insertion of <i>o</i>‐Carborynes into the α‐CH Bond of Tertiary Amines: Synthesis of α‐Carboranylated Amines

Zhao, Da; Zhang, Jiji; Xie, Zuowei

doi:10.1002/ange.201409141

Angewandte Chemie

2014

DOI: 10.1002/ange.201409141

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Regioselective Insertion of o‐Carborynes into the α‐CH Bond of Tertiary Amines: Synthesis of α‐Carboranylated Amines

Da Zhao

Jiji Zhang

Zuowei Xie

Abstract: o-Carboryne can undergo a-C À H bond insertion with tertiary amines, thus affording a-carboranylated amines in very good regioselectivity and isolated yields. In this process, the nucleophilic addition of tertiary amines to the multiple bond of o-carboryne generates a zwitterionic intermediate. An intramolecular proton transfer, followed by a nucleophilic attack leads to the formation of the final product. Thus, regioselectivity is highly dependent upon the acidity of a-C À H proton of tertiary amines. This ap… Show more

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Cited by 3 publications

References 74 publications

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Aryne Insertion into σ Bonds

Asamdi

Chikhalia

2017

Asian J Org Chem

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The synthesis of aryne intermediates from ortho‐(trimethylsilyl)aryl triflates by employing a fluoride source, first reported by Kobayashi′s group, has provided a new avenue for the simultaneous construction of two sigma bonds on a benzene ring by inserting an aryne into the sigma bond in a more‐convenient manner. The generation of ortho‐substituted benzenes through aryne intermediates offers a potent scaffold for the synthesis of bioactive heterocyclic compounds, ligands, and natural products. The main aim of this Focus Review is to highlight the application of Kobayashi′s aryne precursor to the one‐pot synthesis of ortho‐substituted benzenes. Examples include transformations that employ transition‐metal catalysis and those that do not.

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Aryne Insertion into σ Bonds

Asamdi

Chikhalia

2017

Asian J Org Chem

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Facile Synthesis of N‐Carboranyl Amines through an ortho‐Carboryne Intermediate

et al. 2015

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The efficient o-carboryne precursor 1-Li-2-OTf-o-C 2 B 10 H 10 reacts with lithium amides at room temperature to give as eries of N-carboranyl amines in moderate to high isolated yields.T his reaction is compatible with ab road substrate scope from primary to secondary,a lkyl to aryl amines.The reaction mechanism is also proposed on the basis of experimental results and DFT calculations.T his represents the first general and efficient method for the synthesis of 1-NR 1 R 2 -o-carboranes.Amine derivatives are ubiquitous in biology and very important functional units in medicinal chemistry,w hich can be generally synthesized by alkylation of ammonia or amines, reduction of nitriles,azides,orimines,and hydroamination of alkenes or alkynes. [1] On the other hand, ag rowing interest has been directed toward the synthesis of o-carborane derivatives bearing organic nitrogen groups owing to their potential applications in medicinal chemistry [2] and catalysis. [3] Fore xample,c arborane-amino acid or -nucleoside combinations serve as excellent candidates for cancer treatment in boron neutron capture therapy (BNCT). [2b-e,4] Moreover, aminoalkyl-o-carboranes have been extensively employed as ligands for transition metal complexes. [3,5] Despite the recent advances in carborane chemistry,t he straightforward and general synthesis of amino-o-carboranes,inparticular, 1-R 2 No-carboranes,s till represents av ery challenging project. [6] It has been documented that 1-NH 2 -o-C 2 B 10 H 11 can be prepared by reduction of azido-or nitroso-o-carborane or by Curtius rearrangement of the carboranyl amide. [7][8][9] However, unlike organic amines,1 -NH 2 -o-carborane does not undergo alkylation/arylation to give the corresponding 1-RNH-ocarborane or 1-R 2 N-o-carborane. [10] Unfortunately,t here are no other convenient methods to prepare these amines. [6,11] Very recently,wereported that o-carboryne, [12] generated in situ from 1-iodo-2-lithio-o-carborane,c an undergo a-CÀH bond insertion with tertiary amines,a ffording a-carborany-Scheme 1. Reaction of o-carboryne with amines.

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Facile Synthesis of N‐Carboranyl Amines through an ortho‐Carboryne Intermediate

Cheng

Zhang

et al. 2015

Angew Chem Int Ed

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Regioselective Insertion of o‐Carborynes into the α‐CH Bond of Tertiary Amines: Synthesis of α‐Carboranylated Amines

Cited by 3 publications

References 74 publications

Aryne Insertion into σ Bonds

Aryne Insertion into σ Bonds

Facile Synthesis of N‐Carboranyl Amines through an ortho‐Carboryne Intermediate

Facile Synthesis of N‐Carboranyl Amines through an ortho‐Carboryne Intermediate

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