Catalytic site-specific and regioselective (3 + 2) transannulations between 1,2,3-thiadiazoles and allenoates†
Abstract
Allenoates, a type of perpendicularly “strained” surrogate of alkynes, readily transannulate, site-specifically and regio-selectively, with 1,2,3-thiadiazoles in the presence of catalytic Rh(I)/bisphosphine, producing tetrasubstituted thiophenes in a redox-neutral manner. 1,2,3-Thiadiazoles act as masked 1,3-dipoles with nucleophilic sulfur and electrophilic carbon termini.