| Abstract
| - The reaction of dodec-11-ene-1,6-diynes or their heteroatom congeners with a hydrosilanecatalyzed by Rh(acac)(CO)2 at ambient temperature and pressure of CO gives the corresponding fused5-7-5 tricyclic products, 5-oxo-1,3a,4,5,7,9-hexahydro-3H-cyclopenta[e]azulenes or their heteroatomcongeners, 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 fromthe 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 reactionmechanisms are discussed. This novel higher-order cycloaddition reaction has also been successfully appliedto the tricyclization of undeca-5,10-diyn-1-als, affording the corresponding 5-7-5 fused-ring products bearinga seven-membered lactone moiety. Related [2+2+2] tricyclizations of enediyne and diynal substrates arealso discussed. These newly discovered reactions can construct multiple bonds all at once, convertinglinear starting materials to polycyclic compounds in a single step. Thus, these new processes provideinnovative routes to functionalized polycyclic compounds that are useful for the syntheses of natural andunnatural products.
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