A facile entry into the ring system of sativene
Magnetic Resonance Imaging
The mechanism of the dehydrobromination of two isomeric dibromo-cis-4a- methyldecalin-2,5-diones and tribromo-cis-4a-methyldecalin-2,5-dione is described. Treatment of dione (2), with 2 equiv of bromine gave a mixture of dibromides (3) and (4) in a 1:1 ratio. Treatment of (2) with 3.2 equiv of bromine gave tribromide (5) as the major product. Dehydrobromination of (3) and (4), independently with DBU in THF, resulted in the loss of HBr and the exclusive formation of two isomeric tricyclic compounds (6) and (7) respectively. Dehydrobromination of tribromide (5) with DBU gave a mixture of two tricyclic compounds (6) and (8) in an approximate ratio of 1:1. The mechanisms of the formation of the isomeric tricyclic bromoketones (6) and (7) from compounds (3) and (4), and that of (6) and (8) from the tribromide (5) are discussed. Both tricyclic compounds (6) and (8), readily available in good yields from Wieland Miescher ketone (1), have the same carbon skeleton as the sesquiterpene hydrocarbon sativene.