# Mechanochemical Organocatalysis: Do High Enantioselectivities Contradict What We Might Expect?

## TL;DR

This review explores whether high enantioselectivity in organocatalytic reactions is possible using ball milling, which involves intense mechanical energy.

## Contribution

The paper surveys literature to examine the compatibility of enantioselective organocatalysis with mechanochemical ball milling.

## Key findings

- Ball milling can achieve high enantioselectivity in organocatalytic reactions despite its mechanical intensity.
- Comparisons show that ball milling can be as effective as solution-based methods for stereoselective control.
- The review highlights cases where mechanochemical conditions do not hinder enantioselectivity.

## Abstract

Ball mills input energy to samples by pulverising the contents of the jar. Each impact on the sample or wall of the jar results in an instantaneous transmission of energy in the form of a temperature and pressure increase (volume reduction). Conversely, enantioselective organocatalytic reactions proceed through perceived delicate and well‐organised transition states. Does there exist a dichotomy in the idea of enantioselective mechanochemical organocatalysis? This Review provides a survey of the literature reporting the combination of organocatalytic reactions with mechanochemical ball milling conditions. Where possible, direct comparisons of stirred in solution, stirred neat and ball milled processes are drawn with a particular focus on control of stereoselectivity.

Enantioselective mechanochemistry? The ability to achieve high enantioselectivies via organocatalytic reactions using the technique of ball‐milling represents a dichotomy. The technique of milling imparts energy and mixing to the system through collisions between the ball, walls of the milling jar, and the substrate. Here, the literature is surveyed to draw some comparisons to solution‐ and neat‐stirred reaction techniques.