Synthesis and spectroscopic and structural characterization of spiro[indoline-3,3′-indolizine]s formed by 1,3-dipolar cycloadditions between isatins, pipecolic acid and an electron-deficient alkene
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Five new spiro[indoline-3,3′-indolizine]s have been synthesized with high regio- and stereospecificity in one-pot three-component reactions between a substituted indole-2,3-dione, (S)-pipecolic acid and trans-3-benzoylacrylic acid, and subsequently characterized using a combination of elemental analysis, IR and 1H and 13C NMR spectroscopy, mass spectrometry and crystal structure analysis. (1′SR,2′SR,3RS,8a′RS)-2′-Benzoyl-5-fluoro-2-oxo-1′,5′,6′,7′,8′,8a′-hexahydro-2′H-spiro[indoline-3,3′-indolizine]-1′-carboxylic acid, C23H21FN2O4, (I), and (1′SR,2′SR,3RS,8a′RS)-2′-benzoyl-5-methyl-2-oxo-1′,5′,6′,7′,8′,8a′-hexahydro-2′H-spiro[indoline-3,3′-indolizine]-1′-carboxylic acid, C24H24N2O4, (II), are isomorphous, as are (1′SR,2′SR,3RS,8a′RS)-2′-benzoyl-1-methyl-2-oxo-1′,5′,6′,7′,8′,8a′-hexahydro-2′H-spiro[indoline-3,3′-indolizine]-1′-carboxylic acid, C24H24N2O4, (III), and (1′SR,2′SR,3RS,8a′RS)-2′-benzoyl-5-chloro-1-methyl-2-oxo-1′,5′,6′,7′,8′,8a′-hexahydro-2′H-spiro[indoline-3,3′-indolizine]-1′-carboxylic acid, C24H23ClN2O4, (IV). Within each isomorphous pair, the spiro ring systems show some conformational differences. In each of (I) and (II), the molecules are linked into complex sheets by a combination of four types of hydrogen bond, and in each of (III) and (IV), a combination of O—H⋯O and C—H⋯π(arene) hydrogen bonds links the molecules to form a chain of centrosymmetric rings. In (1′SR,2′SR,3RS,8a′RS)-2′-benzoyl-1-hexyl-2-oxo-1′,5′,6′,7′,8′,8a′-hexahydro-2′H-spiro[indoline-3,3′-indolizine]-1′-carboxylic acid, C29H34N2O4, (V), a combination of five hydrogen bonds links the molecules into sheets of alternating R22(16) and R66(46) rings. A mechanism is proposed for the formation of compounds (I)–(V) and some comparisons with related structures are made.
Romo , P E , Quiroga , J , Cobo , J & Glidewell , C 2021 , ' Synthesis and spectroscopic and structural characterization of spiro[indoline-3,3′-indolizine]s formed by 1,3-dipolar cycloadditions between isatins, pipecolic acid and an electron-deficient alkene ' , Acta Crystallographica Section C Structural Chemistry , vol. 77 , no. Part 9 , C77 . https://doi.org/10.1107/S2053229621007142
Acta Crystallographica Section C Structural Chemistry
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DescriptionThe authors thank the Centro de Instrumentación Cientifico-Técnica of the Universidad de Jaén (UJA) and its staff for the data collection, and thank COLCIENCIAS, the Universidad del Valle, the Universidad de Jaén and the Consejería de Economía, Innovación, Ciencia y Empleo (Junta de Andalucía, Spain) for financial support.
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