Chemistry of Amidyl Radicals Produced from N-Hydroxypyridine-2-thione Imidate Esters

Article abstract of DOI:10.1021/jo00070a033

The title radicals precursors were prepared from secondary amides by reaction of the amide with phosgene to give an imidoyl chloride followed by reaction with the sodium salt of N-hydroxypyridine-2-thione.Visible light initiated reactions of these precursors gave amidyl radicals 2 which could react with their precursors to give N-(2-pyridylthio) amides or with t-BuSH to give the parent amide.Radicals 2 containing δ,ε-unsaturation on the acyl or alkyl chain cyclized in a 5-exo fashion to give ultimately γ-lactams and N-acylpyrrolidines, respectively.Tandem 5-exo cyclizations of the N-allyl-4-pentenamidyl radical gave pyrrolizidinone products, and a tandem 5-exo/6-endo reaction sequence of the N-(4-pentenyl)benzamidyl radical gave, ultimately, 3,4-benzoindolizidinone.Several relative rate constants for cyclization and trapping of the amidyl radicals and for intramolecular reactions and trapping of the carbon-centered radicals formed by amidyl radical cyclizations were determined, and these values can be employed in synthetic planning.