Ruthenium-catalyzed oxidative transformations of terminal alkynes to ketenes by using tethered sulfoxides: access to β-lactams and cyclobutanones.

The oxidation of in situ generated Ru vinylidenes to ketenes is realized with tethered sulfoxides. The result is a Ru-catalyzed oxidative transformation of terminal alkynes to highly valuable ketenes. Moreover, the ketenes generated here were shown to undergo characteristic ketene [2+2] cycloaddition reactions with tethered alkenes and external imines, yielding synthetically versatile bicyclic cyclobutanones and β-lactams, respectively.