Facile synthesis of unknown 6,7-dihydrofuro[3,4-<i>c</i>]pyridines and 3,4-diaryloylpyridines from <i>N</i>-homopropargylic β-enaminones

In this paper, we have uncovered a new reaction of N-homopropargylic beta-enaminones, i.e. N-(4-phenyl-3-butynyl)-beta-enaminones. When subjected to a reaction with excess molecular iodine or N-iodosuccinimide in the presence of cesium carbonate, N-homopropargylic beta-enaminones afford 6,7-dihydrofuro[3,4-c]pyridines in low to moderate yields. The generation of two new C/O-C bonds during the reaction leads to the construction of unknown heterobicyclic 5,6-fused ring systems. In some reactions, 3,4-diaryloylpyridines are also observed in low yields. During the formation of 3,4-diaryloylpyridines, a new carbonyl (ketone) group is generated. The synthesized 6,7-dihydrofuro[3,4-c]pyridines and 3,4-diaryloylpyridines may be of use in pharmaceutical and medicinal chemistry as new and novel molecular entities and structural leads.