Dual functionalization of mesoporous organosilicon nanoflowers enhances heterogeneous chemoenzymatic conversion of alkynes toward enantiopure alcohols

Abstract

A tandem chemoenzymatic cascade for the direct synthesis of chiral alcohols from bulk alkynes is promising but challenging, as it couples the gold-catalysed alkyne hydration with an alcohol dehydrogenase-driven asymmetric reduction of the resulting ketones. Herewith two heterogeneous bifunctional catalysts are fabricated for chemocatalytic and biocatalytic steps, respectively. The bi-functionalized chemocatalyst (Au@HS/SO₃H-DON), which possesses both Au NPs and Brønsted acid catalytic sites, exhibits superior catalytic performance and better reusability compared to those of homogeneous Au(III) catalysts. The bi-functionalized biocatalyst (ADH@QA-DON) exhibits enhanced reusability over free ADH and enriches NADH, enhancing the overall catalytic performance. Various chiral alcohols are directly obtained from alkynes with high yields (73%–92%) and enantioselectivity (>99% ee) via tandem cascade reactions catalyzed by bifunctional chemo- and biocatalysts. By fabricating a continuous-flow system, a space–time yield (STY) of 4.69 g L⁻¹ h⁻¹ for (S)-1-phenylethanol can be achieved, which is 6.7-fold higher than that obtained in batch.