Formal Alkenylation and Amination of 2‐Nitrobenzofurans with Fumaric Acid Amide Ester under Metal‐Free Conditions

Abstract

An inorganic base promoted metal‐free formal alkenylation and amination of 2‐nitrobenzofurans is established with fumaric acid amide ester derivatives. The cascade strategy provides the 2‐alkenyl and 3‐amino substituted benzofurans via Michael addition/cyclization/nitrous acid elimination/N‐demethoxylation/C−N bond cleavage and isomerization sequence. The desired 2‐(3‐aminobenzofuran‐2‐yl)malonate derivatives are obtained in moderate‐to‐good yields with high stereoselectivity under mild reaction conditions (up to 71 % yield and >20 : 1 Z : E). The structure of the products is assigned from the single crystal x‐ray structural analysis.