title: Structural consequences of weak interactions in dispirooxindole derivatives.
abstract: Spiro scaffolds are being increasingly utilized in drug discovery due to their inherent three-dimensionality and structural variations, resulting in new synthetic routes to introduce spiro building blocks into more pharmaceutically active molecules. Multicomponent cascade reactions, involving the in situ generation of carbonyl ylides from α-diazocarbonyl compounds and aldehydes, and 1,3-dipolar cycloadditon with 3-arylideneoxindoles gave a novel class of dispirooxindole derivatives, namely 1,1''-dibenzyl-5'-(4-chlorophenyl)-4'-phenyl-4',5'-dihydrodispiro[indoline-3,2'-furan-3',3''-indoline]-2,2''-dione, C44H33ClN2O3, (I), 1''-acetyl-1-benzyl-5'-(4-chlorophenyl)-4'-phenyl-4',5'-dihydrodispiro[indoline-3,2'-furan-3',3''-indoline]-2,2''-dione, C39H29ClN2O4, (II), 1''-acetyl-1-benzyl-4',5'-diphenyl-4',5'-dihydrodispiro[indoline-3,2'-furan-3',3''-indoline]-2,2''-dione, C39H30N2O4, (III), and 1''-acetyl-1-benzyl-4',5'-diphenyl-4',5'-dihydrodispiro[indoline-3,2'-furan-3',3''-indoline]-2,2''-dione acetonitrile hemisolvate, C39H30N2O4·0.5C2H3N, (IV). All four compounds exist as racemic mixtures of the SSSR and RRRS stereoisomers. In these structures, the two H atoms of the dihydrofuran ring and the two substituted oxindole rings are in a trans orientation, facilitating intramolecular C-H···O and π-π interactions. These weak interactions play a prominent role in the structural stability and aid the highly regio- and diastereoselective synthesis. In each of the four structures, the molecular assembly in the crystal is also governed by weak noncovalent interactions. Compound (IV) is the solvated analogue of (III) and the two compounds show similar structural features.
authors.affiliation: X-ray Crystallography Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.
authors.forename: Krishnan
authors.initials: K
authors.lastname: Ravikumar
authors.affiliation: X-ray Crystallography Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Sridhar
authors.affiliation: X-ray Crystallography Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.
authors.forename: Jagadeesh Babu
authors.initials: JB
authors.lastname: Nanubolu
authors.affiliation: Natural Product Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.
authors.forename: Govindaraju
authors.initials: G
authors.lastname: Karthik
authors.affiliation: Natural Product Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.
authors.forename: Basi Venkata Subba
authors.initials: BV
authors.lastname: Reddy
keywords: C—H...O interactions; C—H...π interactions; computational chemistry; crystal structure; cycloaddition; dispirooxoindole; endo conformation; exo conformation; regioselectivity; stereoselectivity; weak interactions; π–π interactions