Palladium(II)-Catalyzed C–H Activation and C–C Coupling/Cyclization of Benzamidine and Terminal Alkynes Using an Internal Oxidant

Abstract

Herein, an efficient palladium(II)-catalyzed C–C coupling/cyclization reaction by directed C–H activation of benzamidine and terminal alkynes has been developed. In this practical and high-yielding process, the C–N bond acts as an internal oxidant. It was found that molecules with both electron-donating and electron-withdrawing substituents were suitable substrates for this transformation, and the expected products were obtained in moderate to excellent yields, but when the benzamidine with ortho-methyl substituent is employed, the benzamidine compound may undergo the [1,5]-hydrogen migration, and then Diels–Alder reaction with terminal alkynes to produce the quinoline compound. The use of a single catalytic system to mediate chemical transformations in a synthetic operation is efficient in building complex structures from simple starting materials in an environmentally benign fashion.

Key words

C–H activation - internal oxidant - C–C bond coupling - terminal alkynes

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