Iron-Catalyzed C–H Alkylation of Heterocyclic C–H Bonds

Babu, Kaki Raveendra; Zhu, Nannan; Bao, Hongli

doi:10.1021/acs.orglett.6b03287

Cited by 77 publications

(33 citation statements)

References 68 publications

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“…In addition to the above-discussed transformations,which are all based on traditional alkylating agents,s everal additional reactions based on other types of reagents have been reported for the direct alkylation of azole derivatives.T hey include carboxylic acids, [78][79][80][81]130] peroxides, [127,131] aldehydes, [86,87] in situ generated iminium ions, [132] N-tosylhydrazones, [133][134][135] benzyl carbonates, [136] diarylmethyl carbonates and pivalates, [137] carboxylic xanthates, [97,98] and tertiary cycloalkanols. [99] Carboxylic acids have indeed been exploited for the alkylation of azoles and were shown to be both attractive and efficient alkylating agents.W hereas the use of photoredox catalysis only allowed the direct alkylation of some specific azoles, [78][79][80][81] Zhaoss ilver-promoted oxidative alkylation of azoles such as (benzo)thiazoles and benzoxazole with alkylcarboxylic acids was shown to be more general, affording the corresponding secondary and tertiary C2-alkylated products in good to excellent yields (Scheme 42).…”

Section: Alkylation With Other Reagentsmentioning

confidence: 99%

“…[127] When used in combination with iron(III) triflate,d iacyl peroxides and alkyl-tert-butylperesters were shown by Bao to be effective reagents for the primary,s econdary,and tertiary alkylation of various azoles with good efficiency[Scheme 43, Eq. [131] Ther eaction mechanism is believed to involve the generation of an azole radical together with reduction of Fe III to Fe II .S ubsequent reduction of the alkyl peroxide by aF e II species then generates an alkyl radical which could finally recombine with the persistent azole radical to deliver the desired alkylated product. [131] Ther eaction mechanism is believed to involve the generation of an azole radical together with reduction of Fe III to Fe II .S ubsequent reduction of the alkyl peroxide by aF e II species then generates an alkyl radical which could finally recombine with the persistent azole radical to deliver the desired alkylated product.…”

Section: Alkylation With Other Reagentsmentioning

confidence: 99%

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Beyond Friedel and Crafts: Directed Alkylation of C−H Bonds in Arenes

2019

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The alkylation of arenes is one of the most fundamental transformations in chemical synthesis leading to privileged scaffolds in many areas of science. Classical methods for the introduction of alkyl groups to arenes are mostly based on the Friedel-Crafts reaction, radical additions, metallation or pre-functionalization of the arene: these methods however suffer from limitations in scope, efficiency and selectivity. Moreover, they are based on the innate reactivity of the starting arene, favoring the alkylation at a certain position and rendering the introduction of alkyl chains at other positions much more challenging. This can be addressed by the use of a directing group facilitating, in the presence of a metal catalyst, the regioselective alkylation of a C-H bond. These directed alkylations of C-H bonds in arenes are overviewed, in a comprehensive manner, in this review article.

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Section: Alkylation With Other Reagentsmentioning

confidence: 99%

Section: Alkylation With Other Reagentsmentioning

confidence: 99%

Beyond Friedel and Crafts: Directed Alkylation of C−H Bonds in Arenes

2019

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“…When used in combination with iron(III) triflate, diacyl peroxides and alkyl‐ tert ‐butylperesters were shown by Bao to be effective reagents for the primary, secondary, and tertiary alkylation of various azoles with good efficiency [Scheme , Eq. (2)] . The reaction mechanism is believed to involve the generation of an azole radical together with reduction of Fe III to Fe II .…”

Section: Alkylation Of Heteroarenesmentioning

confidence: 99%

Beyond Friedel and Crafts: Innate Alkylation of C−H Bonds in Arenes

Evano

Theunissen

2019

Angew Chem Int Ed

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Alkylated arenes are ubiquitous molecules and building blocks commonly utilized in most areas of science where there is a need for small organic molecules. Despite its apparent simplicity, the regioselective alkylation of arenes is still a challenging transformation in a lot of cases. Classical methods for the introduction of alkyl groups on arenes, which include the venerable Friedel-Crafts reaction, radical additions, metallation or pre-functionalization of the arene, as well as alternatives such as the directed alkylation of C-H bonds, still suffer from severe limitations in terms of scope, efficiency and selectivity. This can be addressed by exploiting the innate reactivity of some (hetero)arenes, in which electronic and steric properties, governed (or not) by the presence of one (or multiple) heteroatom(s) ensure high levels of regioselectivity. These innate alkylations of C-H bonds in (hetero)arenes will be overviewed, in a comprehensive manner, in this review article.

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“…Iron-catalyzed decarboxylative alkylation of azoles with carboxylic acids by Bao et al [66] Scheme35. Iron-catalyzed decarboxylative alkylation of azoles with carboxylic acids by Bao et al [66] Scheme35.…”

Section: Miscellaneous Examplesmentioning

confidence: 99%

Iron‐Catalyzed C−O Bond Activation: Opportunity for Sustainable Catalysis

2017

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Oxygen-based electrophiles have emerged as some of the most valuable cross-coupling partners in organic synthesis due to several major strategic and environmental benefits, such as abundance and potential to avoid toxic halide waste. In this context, iron-catalyzed C-O activation/cross-coupling holds particular promise to achieve sustainable catalytic protocols due to its natural abundance, inherent low toxicity, and excellent economic and ecological profile. Recently, tremendous progress has been achieved in the development of new methods for functional-group-tolerant iron-catalyzed cross-coupling reactions by selective C-O cleavage. These methods establish highly attractive alternatives to traditional cross-coupling reactions by using halides as electrophilic partners. In particular, new easily accessible oxygen-based electrophiles have emerged as substrates in iron-catalyzed cross-coupling reactions, which significantly broaden the scope of this catalysis platform. New mechanistic manifolds involving iron catalysis have been established; thus opening up vistas for the development of a wide range of unprecedented reactions. The synthetic potential of this sustainable mode of reactivity has been highlighted by the development of new strategies in the construction of complex motifs, including in target synthesis. The most recent advances in sustainable iron-catalyzed cross-coupling of C-O-based electrophiles are reviewed, with a focus on both mechanistic aspects and synthetic utility. It should be noted that this catalytic manifold provides access to motifs that are often not easily available by other methods, such as the assembly of stereodefined dienes or C(sp )-C(sp ) cross-couplings, thus emphasizing the synthetic importance of this mode of reactivity.

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Iron-Catalyzed C–H Alkylation of Heterocyclic C–H Bonds

Cited by 77 publications

References 68 publications

Beyond Friedel and Crafts: Directed Alkylation of C−H Bonds in Arenes

Beyond Friedel and Crafts: Directed Alkylation of C−H Bonds in Arenes

Beyond Friedel and Crafts: Innate Alkylation of C−H Bonds in Arenes

Iron‐Catalyzed C−O Bond Activation: Opportunity for Sustainable Catalysis

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