Regio- and stereoselective methods for the synthesis of 6′-trifluoro(trichloro)methyl
substituted spiro[acenaphthylene-1,11′-chromeno[3,4-a](thia)pyrrolizidin]-2-ones and spiro[acenaphthylene-1,12′-chromeno[3,4-a]indolizidin]-2-ones have been developed based on the three-component reaction of
3-nitro-2-trifluoro(trichloro)methyl-2H-chromenes with azomethine ylides generated in situ from acenaphthenequinone and cyclic
α-amino acids. The cycloaddition proceeds under mild conditions in ethanol or DMSO,
and only endo-isomers of the products with cis-arrangement of nitro and trifluoromethyl groups are formed. The relative configuration
of cycloadducts is reliably confirmed by X-ray diffraction analysis and by 2D NOESY
spectroscopy.
Key words
3-nitro-2-trifluoro(trichloro)methyl-
2H-chromenes - 1,3-dipolar cycloaddition - azomethine ylides - acenaphthenequinone -
cyclic α-amino acids
