Recyclable gold(I)-catalyzed heterocyclization of ynamides with benzyl or indolyl azides towards 2-aminoindoles or 3-amino-β-carbolines

A highly efficient heterogeneous gold(I)-catalyzed heterocyclization of ynamides with benzyl or indolyl azides has been achieved in 1,2-dichloroethane under mild conditions via a heterogenized α-imino gold carbene intermediate using 5 mol% of SBA-15-anchored strongly hindered NHC-gold(I) complex [IPr-SBA-15-AuNTf2] as the catalyst, delivering a wide range of valuable 2-aminoindoles or 3-amino-β-carbolines in mostly good to excellent yields with high regioselectivity. Furthermore, the new heterogenized NHC-gold(I) complex displays the same catalytic activity as IPrAuNTf2 and is facile to recover by centrifugation of the reaction mixture and can be reused at least seven times without any appreciable drop in its catalytic activity.

Recyclable Copper(I)-Catalyzed Cross-Coupling of Trialkylsilylethynes and N-Tosylhydrazones Leading to the Formation of C(sp)-C(sp3) Bonds

A highly efficient heterogeneous copper(I)-catalyzed cross-coupling of trialkylsilylethynes with N-tosylhydrazones has been achieved in dioxane at 90-110 °C via the Cu carbene migratory insertion with an SBA-15-immobilized l-proline-Cu(I) complex [SBA-15-l-Proline-CuI] as the catalyst and LiO^tBu as the base, leading to the formation of C(sp)-C(sp³) bonds. The reaction generates a wide variety of alkyltrialkylsilylalkynes in moderate to high yields. This new heterogenized copper(I) complex exhibits a comparable catalytic efficiency to homogeneous CuI and can be easily recovered through a simple centrifugation process and is recyclable up to 12 times without a remarkable loss of activity.

Tying Covalent Organic Frameworks through Alkene Metathesis and Supported Platinum as Efficient Catalysts for Hydrosilylation

Recently there has been a great interest in covalent organic frameworks due to their fascinating properties. Current approaches to improve their hydrolytic stability mainly rely on the transformation of the dynamic bonds into strong and irreversible bonds, but these approaches also reduce the versatility of the frameworks. Herein, we would like to demonstrate a solution to this dilemma by forming hierarchical bonds through olefin metathesis to produce highly stable COFs. Our approach allows unprecedented opportunities for post-modification of the inner space through the dynamic imine bonds while maintaining the integrity of the framework. Specifically, we demonstrate an amorphous-to-crystalline transformation. In addition, the porosity can be enhanced by up to 70% after full removal of the amine subunits. Overall, our work provides a new direction for the generation of highly stable while still versatile COFs. Meanwhile, platinum(II) complexes can be supported on BHU-2 (Pt@BHU-2) or BHU-2-Oxidate(Pt@BHU-2-Oxidate) as efficient catalysts for hydrosilylation.