Synthesis of 2,3-Dialkyl-5-hydroxybenzofurans via a One-pot, Three-step Reaction Sequence of 2‑Monosubstituted 1,3-Diketones and 1,4-Benzoquinones

An economical one-pot, three-step
reaction sequence of
readily
available 2-monosubstituted 1,3-diketones and 1,4-benzoquinones has
been explored for the facile access of 2,3-dialkyl-5-hydroxybenzofurans.
By using cheap K2CO3 and conc. HCl as the reaction
promoters, the reaction occurs smoothly via sequential Michael addition,
aromatization, retro-Claisen, deacylation, hemiketalization, and dehydration
processes under mild conditions in a practical manner. Additionally,
an interesting phenomenon was observed during the derivatization studies,
where the dihydroquinoline was converted into tetrahydroquinoline
and quinoline products, respectively, via a disproportionation process.