Rearrangements of Linear Triquinanes to the Angular Isomers
摘要:
Warming substituted linear triquinanes in t-BuOK/t-BuOH resulted in their isomerization to the corresponding angularly fused isomers in good yield (59-84%). An alternate route employs a base-catalyzed intramolecular Michael addition of bicyclo[6.3.0]undecenediones, a class of compounds found to be readily-available from 1-alkenylbicyclo[3.2.0]hepten-7-ones via a "one-pot" sequence of reactions. This method is complementary to the isomerization reaction since it provides access to angular triquinanes not readily available from their linear isomers.
Synthesis of the bicyclo[3.2.0] ring systems from 4-allylcyclobutenones. Intramolecular ketene/alkene cycloadditions
摘要:
A general synthesis of bicyclo[3.2.0]heptenones from 4-allylcyclobutenones is described. The rearrangement is envisaged to involve an electrocyclic ring opening of the cyclobutenone and subsequent intramolecular 2 + 2 cycloaddition of the resulting vinylketene to the nonconjugated allylic alkene moiety. This method is particularly suitable for the synthesis of highly substituted derivatives since the regiochemistry of the substitution pattern is conveniently controlled. The scope of the rearrangement and the mechanism are discussed.