Palladium-catalyzed decarboxylative,decarbonylative and dehydrogenative C(sp2)–H acylation at room temperature
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
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| Title |
Palladium-catalyzed decarboxylative,decarbonylative and dehydrogenative C(sp2)–H acylation at room temperature
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| Creator |
Hossian, Asik
Manna, Manash Kumar Manna, Kartic Jana, Ranjan |
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| Subject |
Chemistry
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| Description |
Over the past few decades, an impressive array of C–H activation methodology has been developed for
organic synthesis. However, due to the inherent inertness of the C–H bonds (e.g. ∼110 kcal mol−1 for the
cleavage of C(aryl)–H bonds) harsh reaction conditions have been realized to overcome high energetic transition states resulting in a limited substrate scope and functional group tolerance. Therefore, the development of mild C–H functionalization protocols is in high demand to exploit the full potential of the C–H activation strategy in the synthesis of a complex molecular framework. Although, electron-rich substrates undergo electrophilic metalation under relatively mild conditions, electron-deficient substrates
proceed through a rate-limiting C–H insertion under forcing conditions at high temperature. In addition,
a stoichiometric amount of toxic silver salt is frequently used in palladium catalysis to facilitate the C–H
activation process which is not acceptable from the environmental and industrial standpoint. We report
herein, a Pd(II)-catalyzed decarboxylative C–H acylation of 2-arylpyridines with α-ketocarboxylic acids
under mild conditions. The present protocol does not require stoichiometric silver(I) salts as additives and
proceeds smoothly at ambient temperature. A novel decarbonylative C–H acylation reaction has also
been accomplished using aryl glyoxals as acyl surrogates. Finally, a practical C–H acylation via a dehydrogenative
pathway has been demonstrated using commercially available benzaldehydes and aqueous hydroperoxides. We also disclose that acetonitrile solvent is optimal for the acylation reaction at room temperature and has a prominent role in the reaction outcome. Control experiments suggest that the
acylation reaction via decarboxylative, decarbonylative and dehydrogenative proceeds through a radical pathway. Thus we disclose a practical protocol for the sp2 C–H acylation reaction.
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| Date |
2017-07-19
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| Type |
Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://www.eprints.iicb.res.in/2739/1/Org._Biomol._Chem.%2C_2017%2C_15%2C_6592%E2%80%936603.pdf
Hossian, Asik and Manna, Manash Kumar and Manna, Kartic and Jana, Ranjan (2017) Palladium-catalyzed decarboxylative,decarbonylative and dehydrogenative C(sp2)–H acylation at room temperature. Organic & Biomolecular Chemistry, 15. pp. 6592-6603. |
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| Relation |
htpp://dx.doi.org/10.1039/c7ob01466j
http://www.eprints.iicb.res.in/2739/ |
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