With the increasing concern for sustainability, the use of environmentally friendly media to perform chemical processes has attracted the attention of many research groups. Among them, the use of water, as the unique solvent for reactions, is currently an active area of research. One process of particular interest is the direct nucleophilic substitution of an alcohol avoiding its preliminary transformation into a good leaving group, since one of the by-products in this approach would be water. The direct substitution of allylic, benzylic, and tertiary alcohols has been achieved through SN
1-type reactions with catalytic amounts of Brønsted or Lewis acids; however, organic solvents are often required. In this review, the pioneering SN
1 approaches performed in pure water and in the absence of a metal based Lewis acid are compiled and discussed.
This is an open access article distributed under the Creative Commons Attribution License
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited