Synthesis of 2,3,4-Trisubstituted Chromans Via Nucleophilic Addition of N-, C-, and SNucleophiles to 3-Nitro-2-Trihalomethyl-2H-Chromenes. Stereochemical and Conformational Preferences

Reactions of N-, C-, and S-nucleophiles with 3-nitro-2-trifluoro(or trichloro)methyl-2H-chromenes proceeded via nucleophilic addition at the double bond to give 2,3,4-trisubstituted chromans in good to moderate yields. Stereochemical and conformational preferences of 2,3,4-trisubstituted chromans were studied.