Another process to construct polysubstituted furan derivatives
is ring transformation.9 Functionalization at the 2- and 5-
positions of furans is readily permitted in chemical transformations,
but similar operations at the 3- or 4-position are
difficult to achieve. Electron-rich furan derivatives like 3-amino
furans are easy to modify by Friedel−Crafts acylation and are
exceptionally useful dienes for use in Diels−Alder reactions,
whereas there are only a few reports of the synthesis of
substituted 3-amino furans.10