1,3-DIPOLAR AND DIELS-ALDER CYCLOADDITION REACTIVITY OF LUMISANTONIN

Some double-bond derivatives of lumisantonin (1) were prepared by its 1,3-dipolar and Diels-Alder cycloaddition reactions. Benzonitrile oxide, α,N-diphenylnitrone, and diazomethane afforded the corresponding 1:1 adducts 2, 3a, 3b, and 4, respectively, but diphenylnitrilimine, phenyl azide, and tosyl azide did not give any adduct. The pyrolysis and photolysis of 4 afforded 1-methyl lumisantonin (5) and 1,2-methylene lumisantonin (6), respectively; 6 was surprisingly stable on heating at 250°. The Diels-Alder reactions with cyclopentadiene, furan, isoprene, and myrcene were investigated, but only cyclopentadiene gave the corresponding 1:1 adduct 8a. In the reactions with isoprene and myrcene, pyrolumisantonin was produced in very low yields as a by-product. © 1968, American Chemical Society. All rights reserved.