Reactions of 3-nitro-2-trihalomethyl-2H-chromenes with C-nucleophiles. Synthesis of 3-nitro-4-(pyrazol-4-yl)-2-trihalomethylchromanes

Abstract

The nucleophilic addition of acetylacetone and ethyl acetoacetate at the double bond of 3 nitro 2 trihalomethyl 2H chromenes in the presence of NaH affords 2,3,4 trisubstituted chromanes containing the β dicarbonyl fragment at position 4. The trans-trans configuration and the enol structure of the reaction products were confirmed by 1 H NMR spectroscopy and X ray diffraction. Treatment of these compounds with hydrazine gives the corresponding 3 nitro 4 (pyrazol 4 yl) 2 trihalomethylchromanes. The reactions of 3 nitro 2 trihalomethyl 2H chromenes with nitromethane and nitroethane in the presence of K 2 CO 3 produce 1,3 dinitro derivatives of the chromane series.

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