Benzofuran and benzofuranone derivatives have been synthesized through exclusive 5-exo-dig intramolecular hydroarylation using the amide-directed, cost-effective, high-valent Cp*Co III -catalytic system. Challenging one-pot, orthogonal CÀH functionalizations using two different electrophiles are also reported to afford polysubstituted benzofurans. Several valuable functional group interconversions along with removal of the amide directing group provide a route to access several diversely functionalized benzofurans. The mechanistic study suggests a reversible cobaltation step is operative here.
Hydroarylation of internal alkynes by cost-effective Co-catalysis, directed by N-tert-butyl amides, is achieved to avail mono- or dihydroarylated amide products selectively in an atom and step economic way. Several important functional groups were tolerated under the reaction conditions, and syn-hydroarylation products were exclusively isolated. Notably, a 4-fold C-H hydroarylation provided a highly conjugated organic framework in one step. Kinetic study with extensive deuterium labeling experiments were performed to support the proposed mechanism.
A high-valent Ir(III)-catalyzed C−H bond functionalization is carried out for the first time on water for the synthesis of a biologically relevant chromone moiety. The C−H activation and annulation of salicylaldehydes with diazocompounds provided the desired chromones. The synthesis of C3-substitution-free chromones has also been demonstrated by a one-pot decarboxylation by employing tert-butyl diazoester. C3 and C5 C−H activations of the product chromone are also carried out under different conditions for further diversification.
An approach towards construction of amide C–N bonds under mild conditions through rhodium(III) catalysis has been explored. Previous waste‐free amidations were generally limited to the condensation of carboxylic acids and amines. In this report, we directly applied amination of the aldehyde C(sp2)–H bond to extend the scope of amidation reactions. The amination shows a wide substrates scope, and several important functional groups were tolerated under the benign reaction conditions. The synthesized amides are important precursors for the preparation of benzoxazinone derivatives, found in various bioactive natural products.q
The stereospecific synthesis of Z-enamides is described in this paper. For the first time, isoxazoles have been employed as electrophiles in C−H functionalization to afford thermodynamically less stable Z-enamides utilizing salicylaldehydes in an atom-and step-economic fashion. The stereochemistry of enamides might originate from the relative disposition of atoms present in isoxazole and the intramolecular hydrogen bonding. The reaction showed excellent scope as several structurally and electronically diverse salicylaldehydes and isoxazoles reacted efficiently.
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