A new synthetic approach to dihydrofuran derivatives via the annulation reaction of β-naphthols and 4-hydroxycoumarins with vinylsulfonium salts has been developed. A variety of dihydrofuran derivatives were prepared in moderate to good yields under mild conditions. The products could be readily transformed to the corresponding furans via the dehydrogenation with DDQ.
A facile and practical approach for
the synthesis of natural coumestans
and derivatives starting from 2′,4′-dihydroxyl-3-arylcoumarins
has been developed. The process involved a seqential intramolecular
dehydrogenation/oxa-Micheal reaction efficiently promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene
at 40 °C under metal- and ligand-free conditions with good functional
group compatibility.
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