Trifluorodiazoethane: A versatile building block to access trifluoromethylated heterocycles

Abstract Trifluoromethylated heterocycles have attracted remarkable interest in the last decades. The beneficial physicochemical and biological properties imparted by the incorporation of trifluoromethyl group into heterocycles have been the key factors to the frequent occurrence of trifluoromethyl group in several heterocycles of pharmaceutical and agrochemical relevance. In consequence, the construction of this class of compounds has become a major subject of research in recent years. In this context, 2,2,2‐trifluorodiazoethane (CF 3 CHN 2 ) has emerged as an important reagent in the synthesis of trifluoromethylated heterocycles, thanks to the versatility of this reagent in undergoing a multitude of synthetic transformations. CF 3 CHN 2 readily participates in [2 + 1]‐, [3 + 2]‐, and [3 + 3]‐cycloaddition reactions, as a trifluoromethyl‐containing dipole, thereby creating new approaches to trifluoromethylated heterocycles. The last decade has witnessed phenomenal growth in this area, and now, several methods are available to access highly functionalized 5‐ and 6‐membered trifluoromethyl‐containing heterocycles. In this review, we aim to demonstrate the use of CF 3 CHN 2 in the preparation of different classes of CF 3 ‐substituted heterocycles, giving emphasis to the past 10 years.