Diastereoselective synthesis of spiro[cyclopropane-1,3′-indolin]-2′-imines <i>via</i> a sequential [1 + 2] annulation reaction of indolin-2-imines with α-aryl vinylsulfonium salts

A sequential [1 + 2] annulation reaction of indolin-2-imines with α-aryl vinylsulfonium salts has been achieved for the first time, leading to a series of functionalized spiro[cyclopropane-1,3'-indolin]-2'-imines in 51-95% yields with high chemoselectivity and diastereoselectivity. The method is easy to manipulate, operates under mild conditions, and shows wide substrate scope with good functional group tolerance. Moreover, some of the selected spiro-annulated products exhibit promising anticancer activity against the A549 cell line, highlighting their potential for application in drug screening.