2-SUBSTITUTED 3-NITRO-2<i>H</i>-CHROMENES IN REACTION WITH AZOMETHINE YLIDE DERIVED FROM NINHYDRIN AND PROLINE: REGIO- AND STEREOSELECTIVE SYNTHESIS OF SPIRO[CHROMENO¬[3,4-<i>a</i>]PYRROLIZIDINE-11,2'-INDE¬NE]-1',3'-DIONES
DOI:
https://doi.org/10.1007/4129Keywords:
3-nitro-2H-chromenes, spiro[chromeno[3, 4-a]pyrrolizidine-11, 2'-indene]-1', 3'-diones, stabilized azomethine ylides, 1, 3dipolar cycloaddition.Abstract
Regio- and stereoselective 1,3-dipolar cycloaddition of stabilized azomethine ylides, generated in situ from ninhydrin and proline, occurred at the double bond activated by nitro group in 3-nitro-2-(trifluoromethyl)- and 3-nitro-2-phenyl-2H-chromenes upon heating in ethanol. This reaction produced high yields of spiro[chromeno[3,4-a]pyrrolizidine-11,2'-indene]-1',3'-diones. The structure of the obtained products was confirmed by the method of X-ray crystallography.