Tf2O-Induced Selective 1,3-Transposition/Cyclization of Ynones in DMF

A chemo and regio-selective system for activating C=O and S=O bonds under transition metal-free conditions is described. Thus, a Tf2O-mediated 1,3-transposition of ynones in DMF has been developed, providing a versatile pathway for the downstream synthesis of diverse five- and seven-membered heterocycles. Furthermore, the catalytic migration of carbonyl functionality conjugated to an alkyne unit is investigated. In the presence of sulfoxide, which undergoes a Pummerer reaction, the in-situ generation of highly reactive sulfonium salts enables efficient access to a wide range of sulfur-containing annulated scaffolds. Importantly, 3-SCF2D chromones were obtained in high yields and D-incorporation. This divergent methodology offers a versatile platform for maximizing molecular complexity and diversity.