Stereoselective hetero-Diels–Alder reaction of 3-nitro-2-trihalomethyl-2H-chromenes with 2,3-dihydrofuran and ethyl vinyl ether under solvent-free conditions

3-Nitro-2-trifluoro(trichloro)methyl-2H-chromenes undergo heterodiene cycloaddition to 2,3-dihydrofuran and ethyl vinyl ether under solvent-free conditions producing novel cyclic nitronates with high stereoselectivity and in good yields. 3,6-Dinitro-2-trifluoromethyl-2H-chromene reacts with two molecules of ethyl vinyl ether to give the tandem [4+2]/[3+2] cycloaddition adduct in 48% yield. The stereochemistry of the products was established based on 2D COSY, NOESY, HSQC, and HMBC experiments and an X-ray diffraction study.

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