SYNTHESIS OF 11H-FUROBENZOPYRANOPYRIDIN-11-ONE AND 6,8-DIMETHYL-10H-PYRANOBENZOFUROPYRIDIN-10-ONE (PYRIDOANGELICINS)

Article abstract of DOI:10.3987/COM-92-6021

11H-Furo<3',2':7,8>benzopyrano<3,4-c>pyridin-11-one (3) was synthesized from 1-benzyl-3-ethoxycarbonylpiperidin-4-one and 2,3-dihydro-4-hydroxybenzofuran (5) by a von Pechmann reaction and subsequent aromatization of the hexahydro derivative (6). 6,8-Dimethyl-10H-pyrano<2',3':4,5>benzofuro<3,2-c>pyridin-10-one (4a) was obtained by dehydrogenation of the tetrahydro derivative (10b).This compound was prepared from piperidinone-O-(4,6-dimethylcoumarin-7-yl) oxime (9b) using acid catalyzed Fischer indole-like reaction.Are also reported and compared the results of the reactions of piperidinone-O-(coumarin-7-yl) oxime (9d) and the corresponding 5-methyl (9e) derivative, in which the rearrangement occurs at both the 8 and the 6 positions.