Divergent Assembly of Functionalized Medium-Sized N , O -Heterocycles from N -(2-Hydroxyethyl)sulfonylamide

The divergent base-mediated formal [4+3] and [4+4] annulation of N-(2-hydroxyethyl)sulfonylamides was described for the preparation of seven- and eight-membered oxazaheterocycles. This strategy exhibited mild conditions, moderate to excellent yields, broad substrate scope, and functional group tolerance. The viability of this synthetic method was confirmed by scale-up reactions and additional transformations. In vitro toxicity experiments revealed that the three kinds of N,O-heterocycles exhibited significant antibacterial activity.