The benzophenone sensitised photochemical reaction of vinylnorcaradiene derivatives 1, 5-(2-methylprop-1-enyl)-3-oxatricyclo[4.4.0.01,5]deca-7,9-dien-4-ones, resulted in the regioselective cleavage of one of the cyclopropyl Ï-bonds to afford the isochroman-3-one derivatives 7.
Acid catalyzed, dehydrative aromatization of 1,7-lactol ring fused and 7-hydroxymethyl norcaradienes: A specific cleavage of the C1C7 bond
A specific cleavage of the C-1-C-7 bond, one of the three sigma-bonds of cyclopropane moiety, of norcaradienes 1 was accomplished by acid catalyzed, dehydrative aromatization of the corresponding lactols to give 2H-pyran derivatives.
Stability of norcaradienes. A delicate control by C-7 substituents
rearrangement. Almost identical product ratios from 2 and 3 suggested the existence of a common biradical as an intermediacy. The kinetic versus thermodynamic control of the rearrangement was achieved by the choice of the substituent (X) in norcaradienes 9.