An Eco-Friendly and Switchable Carbon-Based Catalyst for Protection-Deprotection of Vicinal Diols

Abstract

Even though protection-free protocols represent a key principle of green chemistry, both protection and deprotection routes are indispensable strategies in synthetic pursuits, especially towards highly functionalized pharmaceuticals and agrochemicals, often decorated by promiscuous OH or NH groups, among others. Herein a sustainable carbon-based catalyst is reported that efficiently promotes the protection of 1,2-diols as isopropylidene ketals under heterogeneous conditions, affording products in high conversion and yields. Grafting of sulfonate groups onto the high-surface-area carbon creates a solid acid catalyst with high performance for acetalization under mild thermal conditions. Interestingly, the same catalyst can be employed for the inverse deprotection step leading to the parent diols with comparable efficiency. Along with a detailed catalyst's characterization, critical issues related to catalyst loading, reaction scope, and selectivity were thoroughly optimized. The catalyst can be recycled, and no impurities caused by leaching could be observed.