On the reaction between alkyl isocyanides and 3-benzylidene-2,4-pentanedione. A convenient synthetic route to densely functionalized furans

Alkyl isocyanides undergo a formal [1 + 4] cycloaddition reaction with 3-benzylidene-2,4-pentanedione yielding multiply functionalized furan ring systems in fairly high yields. The H-1 NMR spectrum of 4-acetyl-2-(N-benzylamino)-5-methyl-3-phenylfuran shows an AB pattern for the benzylic methylene protons as a result of a restricted rotation about the bond between the acetyl group and the furan ring, thus giving rise to perpendicular disymmetric planes.