Reactions of 2-Nitro-1H-benzo[f]chromenes and 3-Nitro-1-benzofurans with Nucleophiles

Abstract

2-Nitro-1H-benzo[f]chromenes reacted with alcohols to give a series of 3-alkoxy-2-nitro-2,3-dihy¬dro-1H-benzo[f]chromenes as mixtures of cis and trans isomers. The reaction of 2-nitro-1H-benzo[f]chromenes with cyclic secondary amines and 3-amino-5,5-dimethylcyclohex-2-en-1-one displayed trans diastereoselec¬tivity with the formation of Michael adducts with benzochroman structure. Conjugate addition of substituted anilines to the title chromenes afforded (2-hydroxynaphthalen-1-ylmethyl)-substituted β-nitroenamines. Nucleophilic dearomatization of 3-nitrobenzofurans by the action of primary aromatic amines involved aza- and retro-oxa-Michael reactions, which demonstrated a strong tendency of 3-nitrobenzofurans to undergo opening of the furan ring.