Three structures of dispirooxindole derivatives generated in situ through a three‐component one‐pot strategy with complete regio‐ and stereoselectivity. Issue 8 (16th July 2015) - Ravikumar, Krishnan
Abstract The challenging molecular architecture of spirooxindoles is appealing to chemists because it evokes novel synthetic strategies that address configurational demands and provides platforms for further reaction development. The [3+2] cycloaddition of the carbonyl ylide with arylideneoxindole via a five‐membered cyclic transition state gave a novel class of dispirooxindole derivatives, namely tert‐butyl 4′‐(4‐bromophenyl)‐1′′‐methyl‐2, 2′′‐dioxo‐5′‐phenyl‐4′, 5′‐dihydrodispiro[indoline‐3, 2′‐furan‐3′, 3′′‐indoline]‐1‐carboxylate, C36H31BrN2O, (Ia), 5′‐(4‐bromophenyl)‐1, 1′′‐dimethyl‐4′‐phenyl‐4′, 5′‐dihydrodispiro[indoline‐3, 2′‐furan‐3′, 3′′‐indoline]‐2, 2′′‐dione, C32H25BrN2O3, (Ib), and tert‐butyl 1′′‐methyl‐2, 2′′‐dioxo‐4′‐phenyl‐5′‐(p‐tolyl)‐4′, 5′‐dihydrodispiro[indoline‐3, 2′‐furan‐3′, 3′′‐indoline]‐1‐carboxylate, C37H34N2O5, (Ic). Crystal structure analyses of these dispirooxindoles revealed the formation of two diastereoisomers selectively and confirmed their relative stereochemistry (SSSR and RRRS). In all three structures, intramolecular C—H...O and π–π interactions between oxindole and dihydrofuran rings are the key factors governing the regio‐ and stereoselectivity, and in the absence of conventional hydrogen bonds, their crystal packings are strengthened by intermolecular C—H...π interactions.