Regioselective C5 alkenylation of 2-acylpyrroles <i>via</i> Pd(<scp>ii</scp>)-catalyzed C–H bond activation

Jian-hua, Duan; Mi, Ruijie; Sun, Jing; Zhou, Ming‐Dong

doi:10.1039/c7qo00732a

Cited by 13 publications

(8 citation statements)

References 61 publications

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“…Subjected the cross-coupling products to a second DHR led to C5 substitution with, in the case of the tosylpyrrole, a domino reaction leading to an indole (Scheme 7). (33) In contrast to the above, the DHR of N-(p-NCC6H4CO)-2-acylpyrroles mainly occurred at the C5 (34) In contrast to the above, the DHR of N-(p-NCC 6 H 4 CO)-2-acylpyrroles mainly occurred at the C5 position (Equation (35)) [73]. According to Sun and co-workers, the carbonyl of the protecting group could have a directing effect but "should not be dominant for this C5-alkenylation".…”

Section: (33)mentioning

confidence: 93%

“…We suspect a C5 selectivity favored by coordination of the nitrile moiety to Pd-intermediates. 35The thioether previously used as additive (Scheme 2) also participated in the DHR of N-protected pyrroles (Equation 36 In contrast to the above, the DHR of N-(p-NCC6H4CO)-2-acylpyrroles mainly occurred at the C5 position (Equation (35)) [73]. According to Sun and co-workers, the carbonyl of the protecting group could have a directing effect but "should not be dominant for this C5-alkenylation".…”

Section: (33)mentioning

confidence: 99%

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Pd-Catalyzed Intermolecular Dehydrogenative Heck Reactions of Five-Membered Heteroarenes

Bras

Мuzart

2020

Catalysts

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The Pd-mediated cross-coupling of (hetero)arenes with alkenes may be an effective method for the formation of a C–C bond from two C–H bonds. Discovered by Fujiwara and co-workers in 1967, this reaction led to a number of reports that we firstly highlighted in 2011 (review with references till June 2010) and for which, we retained the name “dehydrogenative Heck reaction”. The topic, especially the reactions of five-membered heteroarenes, has been the subject of intensive research over the last ten years. The present review is limited to these dehydrogenative Heck reactions published since 2010, underlining the progress of the procedures.

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Section: (33)mentioning

confidence: 93%

Section: (33)mentioning

confidence: 99%

Pd-Catalyzed Intermolecular Dehydrogenative Heck Reactions of Five-Membered Heteroarenes

Bras

Мuzart

2020

Catalysts

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“…In 2010, Jafarpour and group developed an atom economical and phosphane‐free palladium‐catalyzed regioselective direct C‐2 arylation of unactivated free NH‐pyrroles (Scheme 5). [37] This protocol utilizes Pd(OH) 2 as catalyst for direct C‐2 arylation of pyrroles. Iodoarenes bearing variety of electron‐withdrawing and electron‐donating substituents were tolerated well under this method.…”

Section: C−h Functionalization Of Pyrrolesmentioning

confidence: 99%

“…The utilized N‐protecting group was promptly removable within the sight of HCl/EtOH under mild conditions. This transformation demonstrated great C5 selectivity with a capacity to bear different acyl phenyl substituted 2‐acyl pyrroles, managing a wide scope of 2,5‐disubstituted pyrrole derivatives as the sole products [37] …”

Section: C−h Functionalization Of Pyrrolesmentioning

confidence: 99%

Recent Advances in Functionalization of Pyrroles and their Translational Potential

Hunjan

Panday

Gupta

et al. 2021

The Chemical Record

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Among the known aromatic nitrogen heterocycles, pyrrole represents a privileged aromatic heterocycle ranging its occurrence in the key component of “pigments of life” to biologically active natural products to active pharmaceuticals. Pyrrole being an electron‐rich heteroaromatic compound, its predominant functionalization is legendary to aromatic electrophilic substitution reactions. Although a few excellent reviews on the functionalization of pyrroles including the reports by Baltazzi in 1963, Casiraghi and Rassu in 1995, and Banwell in 2006 are available, they are fragmentary and over fifteen years old, and do not cover the modern aspects of catalysis. A review covering a comprehensive package of direct functionalization on pyrroles via catalytic and non‐catalytic methods including their translational potential is described. Subsequent to statutory yet concise introduction, the classical functionalization on pyrroles using Lewis acids largely following an ionic mechanism is discussed. The subsequent discussion follows the various metal‐catalyzed C−H functionalization on pyrroles, which are otherwise difficult to implement by Lewis acids. A major emphasize is given on the radical based pyrrole functionalization under metal‐free oxidative conditions, which is otherwise poorly highlighted in the literature. Towards the end, the current development of pyrrole functionalization under photocatalyzed and electrochemical conditions is appended. Only a selected examples of substrates and important mechanisms are discussed for different methods highlighting their scopes and limitations. The aromatic nucleophillic substitution on pyrroles (being an electron‐rich heterocycle) happened to be the subject of recent investigations, which has also been covered accentuating their underlying conceptual development. Despite great achievements over the past several years in these areas, many challenges and problems are yet to be solved, which are all discussed in summary and outlook.

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“…Then, Zhou's group have developed a palladium(II)-catalyzed direct C5 alkenylation of 2-acylpyrroles using various functionalized alkenes as coupling partners. [13] In addition, Matti's, [14] Xu's, [15] and Zhou's group [16] both employed a D-shaped guiding template to perform meta-selective CÀ H olefination (Scheme 1-b). In recent years, palladium-catalyzed non-directed alkenylation has been aggressively developed.…”

Section: Introductionmentioning

confidence: 99%

Palladium‐Catalyzed Pyridine Ligand‐Promoted Non‐Directed C−H Olefination of Phenol Derivatives

et al. 2022

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Herein, we report an undirected ortho-olefination reaction using tri-isobutyl silicon-protected phenol as the substrate, palladium acetate as the catalyst, and inexpensive pyridine derivatives as ligands. Various phenols were tolerated well, affording the olefinated product in moderate to good yields. Importantly, bioactive compounds such as hexyl-methoxyphenol and estradiol were tolerated, highlighting the synthetic importance of this method.

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Regioselective C5 alkenylation of 2-acylpyrroles via Pd(ii)-catalyzed C–H bond activation

Abstract: A Pd(ii)-catalyzed regioselective C5 alkenylation of 2-acylpyrroles to synthesize various C5-alkenylated 2-acylpyrroles using a readily removable N-protecting group is developed.

Cited by 13 publications

References 61 publications

Pd-Catalyzed Intermolecular Dehydrogenative Heck Reactions of Five-Membered Heteroarenes

Pd-Catalyzed Intermolecular Dehydrogenative Heck Reactions of Five-Membered Heteroarenes

Recent Advances in Functionalization of Pyrroles and their Translational Potential

Palladium‐Catalyzed Pyridine Ligand‐Promoted Non‐Directed C−H Olefination of Phenol Derivatives

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