Diastereoselective Synthesis of Functionalized Indoline N,O‐Aminals: Unexpected Water‐Involved Cascade Reaction of 3H‐Indoles and Oxazol‐5‐(4H)ones

Herein, we describe an unexpected TsOH · H 2 O‐mediated domino three‐component reaction of 3 H ‐indoles, oxazol‐5‐(4 H )ones, and water, allowing rapid access to a new family of structurally unique indoline N , O ‐aminals bearing a valuable α‐acylaminoamide moiety in high yields and excellent diastereoselectivities. The scaled‐up experiment and various transformations of the products further demonstrate the utility of this chemistry. Moreover, a preliminary study on the catalytic asymmetric version of this novel 1,2‐difunctionalization reaction is performed.