Directed, DDQ-Promoted Benzylic Oxygenations of Tetrahydronaphthalenes.
Positional preferences for para benzylic oxygenation of tetrahydronaphthalenes by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-aqueous dioxane were investigated by comparing the tetralone products from 6-hydroxy-7-methoxy- and 6-acetoxy-7-methoxy-1,2,3,4-tetrahydronaphthalene. The directing influence by an aromatic substituent on para benzylic oxygenation was in the order OH > OMe > OAc. Consistent with this finding were results obtained from lignan analogues. Treatment of (+)-beta-conidendryl alcohol with DDQ in dry dioxane resulted in the intramolecular bridging by one of two primary hydroxy groups to the benzylic position, giving an oxabicyclo[3.2.1]octane. Similar treatment of (+)-dimethyl-beta-conidendryl alcohol resulted in bridging by the alternate primary hydroxyl group to the benzhydrylic carbon giving an isomeric oxabicyclo[3.2.1]octane.
Ramdayal
Frank D.
FD
Department of Chemistry, Jahn Laboratory, State University of New York, College of Environmental Science and Forestry, Syracuse, New York 13210.
Kiemle
David J.
DJ
LaLonde
Robert T.
RT