TCCA/RSeSeR-Mediated Selenoalkoxy of Allenamides via a Radical Process: Synthesis of Selanyl-allylic N,O-Aminals

An
efficient TCCA (trichloroisocyanuric acid)/RSeSeR-mediated selenoalkoxy
of allenamides for the construction of selanyl-allylic N,OA-aminal
derivatives was developed. The reaction exhibits good functional group
tolerance and high efficiency, affording the products in good to excellent
yields. Mechanistic investigations indicated that a selanyl-allylic
radical intermediate was first formed via the RSe radical added to
the central carbon of allenamides, which subsequently furnished highly
stable selanyl-allylic carbocation intermediate by abstraction of
an electron by the chlorine radical. Moreover, this is the first report
of using selenium reagent (RSeCl) to activate allenamides via a radical
process.