An Efficient and Recyclable Catalyst for N‐Alkylation of Amines and β‐Alkylation of Secondary Alcohols with Primary Alcohols: SBA‐15 Supported N‐Heterocyclic Carbene Iridium Complex

Abstract

A mesoporous silica (SBA-15)-supported pyrimidine-substituted N-heterocyclic carbene iridium complex was prepared and used as a catalyst for both environmentally friendly N-alkylation of amines and b-alkylation of secondary alcohols with primary alcohols. The structure of the supported iridium catalyst was characterized by Fourier transform infrared (FT-IR), 13 C and 29 Si solid-state nuclear magnetic resonance (NMR), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), iridium K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopic analyses which demonstrated that the coordination environment of the iridium centre and the 3-dimensional-hexagonal pore structure of SBA-15 were retained after the immobilization. The catalyst was found to be highly efficient for both kinds of reaction on a wide range of substrates under mild conditions. Moreover, the sup-ported iridium catalyst was obviously superior to the unsupported one in the N-alkylation of aniline and b-alkylation of 1-phenylethanol with benzyl alcohol as substrate, which indicated that not only the iridium complex moiety but also the support material contributed to the catalytic activity of the supported iridium catalyst in these reactions. The supported iridium catalyst can be easily recycled by simple washing without chemical treatment, and exhibited excellent recycling performance without notable decrease in catalytic efficiency even after twelve test cycles for N-alkylation of aniline with benzyl alcohol, nine cycles for N-alkylation of different amines with different alcohols, and eight cycles for b-alkylation of 1phenylethanol with benzyl alcohol, respectively.

C‐Alkylation of Ketones and Related Compounds by Alcohols: Transition‐Metal‐Catalyzed Dehydrogenation

“…AS BA-15-supported Ir/NHC complex was also reported as the catalyst for b-alkylation of secondary alcohols with primary alcohols. [87] AP t/q-Al 2 O 3 catalyst efficiently promoted the 3-alkylation of indoles [Eq. (27)].…”

Direct Au-Ni/Al 2 O 3 catalysed cross-condensation of ethanol with isopropanol into pentanol-2

“…The fermentation mixture of the IBE conversion also did not lead to C 5 product formation. The condensation of secondary alcohols with primary alcohols thus effectively catalysed by homogeneous base and homogeneous/heterogeneous transition metal systems [9,27,28] but never a pure heterogeneous catalytic system.…”

“…The conversion of ethanol into n-butanol over purely heterogeneous catalysts has been reported in several publications and patents [8][9][10][11][12][13][14][15][16][17][18]. Generally, the reaction temperature varies from 200 up to 450 • C with a relatively low conversion (e.g., 10%-20%) and a selectivity approaching 70%.…”

Activity and Recyclability Improvement Through Adjusting the Tethering Strategy for Pd-Catalyzed Suzuki–Miyaura Coupling Reaction of Aryl Chlorides

“…To the best of our knowledge, successful examples of highly active coupling of aryl chlorides with arylboronic acids were rare [41]. Based on our previous work [42][43][44][45][46][47], we designed four immobilized catalysts with different Pd-NHC moieties using SBA-15 as support. Our result demonstrated that both catalytic activities and recycling performance were improved through adjusting the tethering strategy of ligands to supports.…”