An Efficient <i>N</i>‐Arylation of Heterocycles with Aryl‐, Heteroaryl‐, and Vinylboronic Acids Catalyzed by Copper Fluorapatite

Kantam, M. Lakshmi; Venkanna, Gopaladasu T.; Kumar, K. B. Shiva; Subrahmanyam, Vura Bala

doi:10.1002/hlca.200900326

Cited by 13 publications

(7 citation statements)

References 21 publications

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“…Several methods have been developed for the arylation of imidazoles; for instance, the Ullman53 and Buchwald54 coupling reactions. These methodologies have been applied in the arylation of imidazoles with aryl halides,55,56 aryllead(IV) reagents,57 arylboronic acids,58,59 and trifluoroaryl borates 60. Despite the tautomeric equilibrium of imidazoles, several N‐arylation reactions were reported to have good chemoselectivities toward the ϵ‐nitrogen atom of backbone‐functionalized imidazoles 55,57.…”

Section: Resultsmentioning

confidence: 99%

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

et al. 2015

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We have studied the use of amino acid histidine as a precursor for N-heterocyclic carbene (NHC) ligands. This natural amino acid possesses an imidazole substituent, which makes it an interesting NHC precursor that contains both an acid and an amino functionality. These functionalities may be used for further tuning of NHC complexes. We have developed routes for the synthesis of symmetric and dissymmetric alkyl, benzyl, and aryl-substituted histidinium salts.[a] Molecular Scheme 3. Synthesis of symmetrically substituted benzylic histidinium bromides. The Cyclic Urea ApproachSubsequently, we employed the cyclic urea approach, which allows the synthesis of dissymmetrically substituted histidinium salts and further tuning of the properties of the NHC metal complex. This is not straightforward because histidine has two tautomeric forms, which means that the δ-and the ε-nitrogen of the imidazole possess both imine and amine character (compound 4, Scheme 5). [20] Therefore, mixtures of regioisomers are obtained when the imidazole is reacted with one equivalent of an electrophile. To obtain the desired dissymmetrically substituted histidinium salts, we applied a route based on the report by Hodges and Chivikas, [17] and was improved by Brégeon et al. [30] (Scheme 4). Scheme 4. The cyclic urea route toward dissymmetrically substituted histidinium salts.This cyclic urea route induces regioselectivity because only the six-membered cyclic urea 5 can be formed. The second nitrogen atom can then be functionalized selectively through nucleophilic substitution. Subsequently, the R 1functionalized urea compounds can be ring-opened by reaction with an alcohol, which liberates the δ-nitrogen atom of the imidazole, and provides a carbamate-protected amine. The use of tBuOH affords the Boc-protected histidine, Eur. J. Inorg. Chem. 2015, 982-996

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Section: Resultsmentioning

confidence: 99%

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

et al. 2015

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“…Complete stereoselectivity was achieved, since only the (Z)-isomer of 1-styrylpyrazole was formed, indicating that anti-addition, via a concerted mechanism, in which pyrazole nitrogen attacks the alkyne from the side opposite to a coordinated Lewis acid (LA), is involved as a key step in the reaction process [55]. [53]. The lower yield (70%) for the coupling with 3,5-dimethyl-1H-pyrazole 17 (R 1 = R 2 = Me) was attributed to the steric hindrance caused by the methyl groups.…”

Section: N-styrylation Of Pyrazoles With Activated and Non-activated mentioning

confidence: 99%

“…In 2010, Kantam et al synthesized ( E )-1-styrylpyrazoles in a simple and efficient way, by the cross-coupling reaction of pyrazoles 17 with styrylboronic acid 18 using a recyclable heterogeneous Cu-exchanged fluorapatite (CuFAP) catalyst, under base-free conditions ( Scheme 1 ) [ 53 ]. The lower yield (70%) for the coupling with 3,5-dimethyl-1 H -pyrazole 17 (R 1 = R 2 = Me) was attributed to the steric hindrance caused by the methyl groups.…”

Section: Synthesis Of Styrylpyrazolesmentioning

confidence: 99%

“…The lower yield (70%) for the coupling with 3,5-dimethyl-1 H -pyrazole 17 (R 1 = R 2 = Me) was attributed to the steric hindrance caused by the methyl groups. When the reaction was performed in the absence of air, no coupled product was obtained, since O 2 is involved in the oxidation of Cu(I) to Cu(II), which is the active species in the reaction mechanism [ 53 ].…”

Section: Synthesis Of Styrylpyrazolesmentioning

confidence: 99%

“… Cross-coupling reactions of pyrazoles 17 with styrylboronic acid 18 to produce ( E )-1-styrylpyrazoles 19 [ 53 ]. …”

Section: Figures and Schemesmentioning

confidence: 99%

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Styrylpyrazoles: Properties, Synthesis and Transformations

et al. 2020

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The pyrazole nucleus and its reduced forms, pyrazolines and pyrazolidine, are privileged scaffolds in medicinal chemistry due to their remarkable biological activities. A huge number of pyrazole derivatives have been studied and reported over time. This review article gives an overview of pyrazole derivatives that contain a styryl (2-arylvinyl) group linked in different positions of the pyrazole backbone. Although there are studies on the synthesis of styrylpyrazoles dating back to the 1970s and even earlier, this type of compound has rarely been studied. This timely review intends to summarize the properties, biological activity, methods of synthesis and transformation of styrylpyrazoles; thus, highlighting the interest and huge potential for application of this kind of compound.

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Beyond Ullmann–Goldberg Chemistry: Vinylation, Alkynylation, and Allenylation of Heteronucleophiles

Jouvin¹,

Evano²

2013

Copper‐Mediated Cross‐Coupling Reactions

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An Efficient N‐Arylation of Heterocycles with Aryl‐, Heteroaryl‐, and Vinylboronic Acids Catalyzed by Copper Fluorapatite

Cited by 13 publications

References 21 publications

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

Styrylpyrazoles: Properties, Synthesis and Transformations

Beyond Ullmann–Goldberg Chemistry: Vinylation, Alkynylation, and Allenylation of Heteronucleophiles

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