Three structures of dispirooxindole derivatives generated in situ through a three-component one-pot strategy with complete regio- and stereoselectivity.

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.