Chemoselective reduction of α,β-unsaturated aldehydes and ketones over mesoporous B(OⁱPr)₃–MCM-41 catalyst via MPV reduction process: preparation, characterization and catalytic application

Abstract

Boron alkoxide-containing ordered mesoporous silica material (B(OⁱPr)₃–MCM-41) was prepared by the grafting method. The obtained B(OⁱPr)₃@MCM-41 composite materials were fully characterized in details by PXRD, FT-IR-, ¹¹B-NMR-, ²⁹Si-NMR-, ¹³C-NMR-spectroscopies, scanning electron microscopy, EDX, transmission electron microscopy techniques, N₂ adsorption–desorption isotherms and Inductively coupled plasma-optical emission spectroscopy analyses, demonstrating the successful homogenous distribution of the B(OⁱPr)₃ catalyst in the MCM-41 support. The as-prepared new materials were successfully applied in the chemoselective Meerwein–Ponndorf–Verley reduction of α,β-unsaturated carbonyl compounds. In the reduction of α,β-unsaturated aldehydes and ketones, which can not be reduced by usual catalysts, a very high selectivity, especially for the reduction of allylic aldehydes and ketones could be obtained. In most cases no side product formation could be observed. The catalyst was found to be encouraging as a heterogeneous catalyst as the yield was almost unchanged after up to six cycles. No leaching of the grafted boron tri-isopropoxide into the reaction mixture could be detected.