title: Silicon-initiated carbonylative carbotricyclization and [2+2+2+1] cycloaddition of enediynes catalyzed by rhodium complexes.
abstract: 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.
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA.
authors.forename: Bibia
authors.initials: B
authors.lastname: Bennacer
authors.forename: Masaki
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Seung-Yub
authors.initials: SY
authors.lastname: Lee
authors.forename: Iwao
authors.initials: I
authors.lastname: Ojima
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis*; D003500:Cyclization; D007659:Ketones / Q000138:chemical synthesis; D017655:Silicon Compounds / Q000737:chemistry*
chemical_list: D000475:Alkenes; D000480:Alkynes; D001643:Bridged Bicyclo Compounds; D007659:Ketones; D017655:Silicon Compounds