Radical leaps in radical chemistry. Part 1

Abstract

Since the final decade of the twentieth century, radicals – once regarded as highly reactive and difficult-to-control intermediates – have become indispensable tools of modern synthetic organic chemistry. Classical methods of radical generation, including tributyltin hydride chemistry, the Barton reaction, and atom- or group-transfer processes, have matured into standard synthetic methodologies. More recently, however, new radical precursors, mechanistic insights, and catalytic strategies have dramatically expanded both the scope and the synthetic potential of radical reactions, fundamentally reshaping their role in retrosynthetic planning. This Review highlights some of the most significant conceptual and methodological advances in carbon–carbon bond-forming radical reactions achieved during the past two decades. Electrochemical methods are beyond the scope of this article. Owing to its length, the Review is presented in two consecutive parts. Part 1 comprises the Introduction, six topics illustrating recent advances in "classical" radical chemistry, and five topics describing conceptual developments associated with visible-light photocatalysis. Part 2 covers twelve additional visible-light-photocatalytic transformations together with applications of radical chemistry in total synthesis.