Oxepines from Pyrylium Salts and Diazo Esters. Cycloaddition Behavior toward 4-Phenyl-1,2,4-triazoline-3,5-dione

Article abstract of DOI:10.1021/jo00226a024

Electrophilic diazoalkane substitution of the diazo esters 7a and b with 2,4,6-trimethylpyrylium tetrafluoroborate (6a) results in the formation of the 4-(diazomethyl)-4H-pyrans 8a and b as well as the 1H-1,2-diazepines 13a and b.The latter are formed by