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Keywords:

  • azides;
  • copper;
  • heterogeneous catalysis;
  • metal–organic frameworks;
  • multicomponent reactions

Abstract

A reliable procedure for the synthesis of oxysulfonyl azides has been developed and applied to the three-component coupling reactions of azides, alkynes, and amines catalyzed homogeneously by CuI, which led to the formation of N-oxysulfonyl amidines with good yields. To fully evaluate the catalytic activity towards this coupling reaction, two coordination frameworks, namely, Cu2I2(PDIN) without micropores and Cu2I2(BTTP4) with micropores (PDIN=1,4-phenylene diisonicotinate, BTTP4=benzene-1,3,5-triyltriisonicotinate), were prepared by a facile one-pot reaction as heterogeneous catalysts. Catalytic results showed that nonporous Cu2I2(PDIN) was almost inactive for the three-component coupling reaction, whereas microporous Cu2I2(BTTP4) was an efficient heterogeneous catalyst for the synthesis of N-oxysulfonyl amidines. Furthermore, porous Cu2I2(BTTP4) displayed a shape-selective performance with respect to the alkyne substrates, and aromatic alkynes were preferable to aliphatic alkynes. The location of the catalytically active sites in the Cu2I2(BTTP4) framework has been studied by a series physical techniques, which includes powder XRD, CO2 gas adsorption, IR spectroscopy, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy, which suggests that the catalytic sites are not only on the external surface but also inside the micropores.