Transition‐Metal Catalyzed, Thermally Driven [2π+2π]‐Cycloadditions of Olefins and Alkynes

The [2+2]‐cycloaddition of olefins and alkynes stands out as a versatile and atom‐economical strategy for synthesizing cyclobutane and cyclobutene building blocks, which are challenging to access through other synthetic methods. While photochemical approaches have traditionally dominated this field, thermally‐driven methods employing transition metals offer distinct advantages, including decreased reliance on pre‐functionalized substrates and improved scalability. This review explores the underlying principles of metal‐catalyzed [2+2]‐cycloadditions and highlights recent advances in thermally‐driven approaches for the efficient synthesis of cyclobutane and cyclobutene frameworks. Particular attention is given to electronically unbiased substrates, which remain a significant challenge for photochemical approaches.