Silicon-Initiated Carbonylative Carbotricyclization and [2+2+2+1] Cycloaddition of Enediynes Catalyzed by Rhodium Complexes

摘要

The reaction of dodec-11-ene-1,6-diynes or their heteroatom congeners with a hydrosilane catalyzed by Rh(acac)(CO)_2 at ambient temperature and pressure of CO gives the corresponding fused 5-7-5 tricyclic products,5-oxo-1,3a,4,5,7,9-hexahydro-3H-cyclopenta[e]azulenes or their heteroatom congeners,in excellent yields through a unique silicon-initiated cascade carbonylative Carbotricyclization (CO-SiCaT) process.It has also been found that the 5-7-5 fused tricyclic products can be obtained from the same type of enediynes and CO through a novel intramolecular [2+2+2+1] cycloaddition process.The characteristics of these two tricyclization processes and the fundamental differences in their reaction mechanisms are discussed.This novel higher-order cycloaddition reaction has also been successfully applied to the tricyclization of undeca-5,10-diyn-1-als,affording the corresponding 5-7-5 fused-ring products bearing a seven-membered lactone moiety.Related [2+2+2] tricyclizations of enediyne and diynal substrates are also discussed.These newly discovered reactions can construct multiple bonds all at once,converting linear starting materials to polycyclic compounds in a single step.Thus,these new processes provide innovative routes to functionalized polycyclic compounds that are useful for the syntheses of natural and unnatural products.