Recent Developments in Titanium, Nickel, and Other First-Row Transition Metal-Catalyzed Hydro(amination/aminoalkylation), Oxidative Amination, and Carboamination Reactions

Amination reactions provide important routes to medicinally relevant synthons. While hydroamination, hydroaminoalkylation, and carboamination are readily achieved by transition metal catalysis, these reactions often rely on precious metals. The replacement of these metals with earth-abundant elements that exhibit comparable catalytic activity has emerged as a core goal of modern catalysis research. In the field of catalytic amination, titanium presents an ideal candidate for this goal: it is abundant, nontoxic, affordable, and exhibits diverse reactivity with unsaturated substrates. Most recently, catalytic cycles involving masked low-valent Ti(II) species have enabled a highly modular [2 + 2 + 1] coupling of unsaturated substrates and amines. These oxidative amination reactions provide efficient routes to nitrogen heterocycles including pyrroles and pyrazoles. This review will highlight recent developments in titanium- and other first-row transition metal-catalyzed hydro(amination/aminoalkylation), oxidative amination, and carboamination reactions, with a focus on mechanism, substrate and product scope, and regioselectivity. Reactions of interest include [2 + 2 + 1] cycloaddition, oxidative ring-opening amination, diamination, hydroaminoalkylation with aminopyridinato and formamidinato titanium catalysts, and directed umpolung carboamination. While the field of titanium-catalyzed amination chemistry is regularly reviewed, it is also rapidly growing, and this work aims to provide a timely update covering developments from primarily 2018–2025.