Brønsted acid-mediated annulations of pyrroles featuring N-tethered α,β-unsaturated ketones and esters: total syntheses of (±)-tashiromine and (±)-indolizidine 209I

This study provides the first report of the construction of tetrahydroindolizines and tetrahydropyrrolo [1,2-a]azepines via Brønsted acid-mediated annulation of pyrroles featuring N-tethered α,β-unsaturated esters. In addition, the Brønsted acid-catalyzed cyclization of pyrroles featuring pendant α,β-unsaturated ketones was applied to complete total syntheses of the indolizidine alkaloids (±)-tashiromine and (±)-indolizidine 209I.