Deuteration is a crucial tool for drug ADME studies and biomolecular analysis techniques. It can improve the metabolic stability, pharmacokinetics and toxicity profile of drugs. The landmark ruling by the U.S. Food and Drug Administration (FDA) classing deuterated drugs as new chemical entities (NCEs) has also added significant commercial importance to these compounds. The development of new methods to selectively incorporate deuterium into drug molecules has therefore become an important field of study. A substrate class of particular interest in this area are nitrogen heterocyclesincluding indolesdue to their importance in many small-molecule drugs. Scheme 1. Regioselectivity in indole-deuteration reactions.