Selective Continuous‐Flow Syntheses of 1,2‐Diols From Alkenes by Utilizing a Dual Functionality of Titanium Silicalite‐1 Catalyst in the Presence of Hydrogen Peroxide Without Carboxylic Acids

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Selective syntheses of 1,2‐diols from alkenes have traditionally relied on carboxylic acids and various oxidants, which often co‐produce hazardous byproducts. This report describes a simple, carboxylic‐acid‐free method to produce various aliphatic and cyclic diols from their corresponding alkenes in 51–96% isolated yields using 2.0 wt% aqueous hydrogen peroxide (H 2 O 2 ). We developed a tandem continuous‐flow process that exploits the dual functionality (peroxo‐species formation and Lewis acidity) of a titanium silicalite‐1 (TS‐1) catalyst. In this system, alkenes undergo H 2 O 2 epoxidation followed by in situ hydration to yield the desired 1,2‐diols. Optimal reaction conditions, including the use of a ternary mixed solvent (EtOH: i PrOH:MeCN = 1:1:1), were established through probe reactions and kinetic studies. Furthermore, catalyst degradation was rigorously analyzed using dynamic nuclear polarization‐nuclear magnetic resonance. The long‐term stability of the process was demonstrated by the continuous synthesis of 4‐phenylbutane‐1,2‐diol for 200 h, maintaining an average yield of over 91% (22.2 g isolated).

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