A Transition-Metal-Free and Base-Mediated Carbene Insertion into Sulfur-Sulfur and Selenium-Selenium Bonds: An Easy Access to Thio- and Selenoacetals

A transition-metal-free and base-mediated carbene insertion across sulfur-sulfur and selenium-selenium bonds has been developed by employing N-tosylhydrazone as a stable and safe carbene precursor. The ylide formation from carbene followed by Stevens rearrangement are considered to be the key steps. This thiol and selenol-free protocol delivers thioacetals and selenoacetals in good to excellent yields in short reaction time with good functional group tolerance. A one-pot synthesis involving insitu generation of tosylhydrazone has also been demonstrated.