METALLKATALYSIERTE ZERSETZUNG VON 4-DIAZOMETHYL-4H-PYRANEN - EIN NEUER ZUGANG IN DAS OXEPINSYSTEM

Article abstract of DOI:10.1016/S0040-4039(00)87867-3

Electrophilic diazoalkane substitution of lithiated diazomethyl compounds (5) with the pyrylium salt 4 leads to the formation of the hitherto unknow 4-diazomethyl 4H-pyranes 6.Their decomposition with catalytic amounts of μ-allyl palladium chloride (dimer) in benzene is followed by ring enlargement to the oxepines 8, which are not in equilibrium with the valence tautomeric benzene oxides 7.