Construction of C2‐Spirocyclopropyl‐Indolin‐3‐Ones through Base‐Promoted [2+1] Annulation Reaction of Indolin‐3‐ones with Bromosulfonium Salts

A simple base‐promoted [2+1] annulation of indolin‐3‐ones and bromosulfonium salts has been developed in this article. This strategy uses simple and easily prepared indolin‐3‐ones 1 as C1 synthons and bromosulfonium salts 2 as C2 synthons under mild reaction conditions, and 33 examples of C2‐spirocyclopropyl‐indolin‐3‐ones were obtained with up to 99 % yield and >20 : 1 dr. A simple and efficient base‐promoted [2+1] annulation reaction has been developed for the synthesis of the structural diversity C2‐spirocyclopropyl‐indolin‐3‐ones. This [2+1] annulation process using simple and easily prepared nucleophilic indolin‐3‐ones (as C1 synthons) and bromosulfonium salts (as C2 synthons) as substrates, and realized the synthesis of C2‐spirocyclopropyl‐indolin‐3‐ones with up to 99 % yield and >20 : 1 dr.