Ultrasound-assisted, ZnBr2-catalyzed regio- and stereoselective synthesis of novel 3,3′-dispiropyrrolidine bisoxindole derivatives via 1,3-dipolar cycloaddition reaction of an azomethine ylide

Abstract

Ultrasound irradiation in presence of 20% ZnBr2 effectively promotes regio-and stereo-selective cycloaddition reaction of azomethine ylide with a series of (E)-3-benzylideneindolin-2-ones to afford 3,3′-dispiropyrrolidine bisoxindole derivatives in excellent yields in methanol at room temperature. The factors affecting the cycloaddition reaction, for example solvent, catalyst, ultrasonic irradiation, are examined in detail to find the mildest conditions and highest reaction yields. The structure and stereochemistry of cycloadducts were determined by spectroscopic data and confirmed by X-ray crystallographic analysis.

Adventures in the Chemistry of Multicomponent and Domino Reactions

“…The reaction of 9 with isatin ( 10 c ) and 3‐alkylidene‐2‐oxindoles 8 a – l afforded dispiro[indole‐3,2′‐pyrrolidine‐3′,3′′‐indole]‐2,2′′(1 H ,1′′ H )‐diones 13 a – l (Scheme 6). [13] The products again contain three asymmetric carbon atoms located next to each other and were formed with excellent 1,2‐diastereoselectivity. The products are formed by reaction of 9 with the keto group of 10 c to form a nitrogen ylide which undergoes [3+2] cycloaddition with 8 a – l .…”