An Unconventional Sulfur-to-Selenium-to-Carbon Radical Transfer: Chemo-and Regioselective Cyclization of Yne-Ynamides
An uncommon sulfur→selenium→carbon radical transfer process is employed to develop an unprecedented selenyl radical-mediated regioselective cyclization of yne-tethered-ynamides. Density functional theory studies and HRMS experiments are used to establish a reactivity scale between thiyl and selenyl radicals. The unique features of this transformation include, 1) the chemoselective reactivity of RSe• over RS•, 2) regioselective RSe• attack on alkyne over ynamide, 3) 5-exo-dig cyclization of yne-ynamide to unusual 4-selenyl-pyrroles, and 4) green synthetic method. The reaction of methyldiselenide with yne-ynamides to methylselenopyrroles is also described.