Oxidative Generation and Reactivity of the Cyclopropyl Radical From a Martin Silicate

The controlled generation of the unsubstituted ("naked") cyclopropyl radical remains a long-standing challenge due to the difficulty of finding effective precursors and reaction conditions that are easy to implement, as well as its high reactivity. Here we report an oxidative photoredox strategy that enables direct access to the cyclopropyl radical from the easily prepared cyclopropyl Martin silicate. In contrast to prevailing reductive approaches (NHP esters, halides), this method eliminates sacrificial metal reductants and enables two distinct transformations: (i) Giese-type additions to electron-deficient alkenes and diazenes, and (ii) dual Ni/photoredox C(sp³)-C(sp²) couplings delivering arylcyclopropanes. The protocol exhibits broad functional-group tolerance and provides rare experimental insight into the philicity and reactivity profile of the unsubstituted cyclopropyl radical. Mechanistic studies have identified inefficient radical capture due notably to competitive hydrogen atom transfer (HAT) from the solvent, while investigations with functionalized silicates revealed structure-reactivity trends supported by X-ray crystallography and DFT calculations. Together, these findings expand the frontiers of cyclopropyl radical chemistry and establish Martin silicates as versatile precursors for difficult-to-access radical species in synthesis.