Coupling-Isomerization-Stetter and Coupling-Isomerization-Stetter-Paal-Knorr Sequences - A Multicomponent Approach to Furans and Pyrroles

Abstract

2,3,5-Trisubstituted furans 6 and 1,2,3,5-tetrasubstituted pyrroles 8 can be synthesized in good yields in a one-pot three-step three- or four-component process by a coupling-isomerization-Stetter-Paal-Knorr sequence of an electron-poor (hetero)aryl halide 1, a terminal propargyl alcohol 2, an aldehyde 3, and, in the case of pyrroles, a primary amine 7. All novel furans and pyrroles exhibit a strong blue fluorescence with considerable Stokes shifts.