The first example of the palladium-catalyzed sequential nucleophilic addition followed by an intramolecular cyclization of functionalized nitriles with arylboronic acids has been achieved, providing an efficient synthetic pathway to access structurally diverse isoquinolines and isoquinolones. This methodology has also been successfully applied to the total synthesis of the topoisomerase I inhibitor CWJ-a-5 (free base).
A novel
metal-free catalysis protocol for the synthesis of 1,2-diarylpyrazolo[5,1-b]quinazolin-9(1H)-ones via intramolecular
oxidative C–H amination of (E)-3-(arylamino)-2-styrylquinazolin-4(3H)-ones has been developed in moderate to good yield. The
method shows good functional group tolerance. The presented approach
offers a new synthetic pathway toward the core structures of 2,3-fused
quinazolinones. Moreover, the present synthetic route can be readily
scaled up to gram quantity without difficulty. A possible mechanism
involves a seleniranium ion followed by three-membered ring opening
to form the C–N bond.
An efficient protocol to construct 2-arylindoles was developed through palladium-catalyzed tandem addition/cyclization of potassium aryltrifluoroborates with aliphatic nitriles in aqueous medium. The use of water as the reaction medium makes the synthesis process environmentally benign. A plausible mechanism for the formation of 2-arylindoles involving sequential nucleophilic addition followed by an intramolecular cyclization is proposed. Moreover, the utility of this catalytic tandem transformation was also demonstrated in an efficient gram-scale synthesis. This method provides an alternative synthetic tool for accessing a more diverse array of 2-arylindoles.
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