Danièle Choueiry

Zirconium-catalyzed carboalumination of alkynes and enynes as a route to aluminacycles and their conversion to cyclic organic compounds

Aluminacyclopentenes, obtainable via Zr-catalyzed cyclic carboalumination with Et3Al and alkynes or enynes, can be converted to the corresponding cyclopentenones and alkenylcyclopropanes by treatment with CO2 and BrCH2OCH3, respectively.

Zirconium catalyzed CC bond formation reaction of conjugated diynes with EtMgBr

The carbon-carbon bond formation reactions of diynes with EtMgBr can be catalysed by Cp2ZrCl2. The final products, magnesiated enynes, readily undergo stereoisomerization to give a mixture of (E) and (Z) isomers. The stoichiometric reaction of diynes with ethylene zirconocene gives zirconacyclopentenes with alkynyl substituents in the α position with high regioselectivities.

Zirconium-catalyzed and zirconium-promoted cyclization reactions of non-conjugated dienes with alkylmagnesium halides to give cycloalkylmethylmagnesium derivatives☆

Abstract The stoichiometric reaction of certain non-conjugated dienes with n-Bu 2 ZrCp 2 provides the corresponding zirconabicycles, such as trans -3-bis(cyclopentadienyl)zirconabicyclo[3.3.0]octane, that can be fully characterized by spectroscopic means. Their treatment with EtMgBr or n-BuMgCl in THF gives the corresponding monocyclic monomagnesium derivatives along with the corresponding alkene-ZrCp 2 derivatives in high yields. In cases where the Grignard reagent is either sterically hindered or lacking β-H, little or no reaction may occur, although some, e.g., s -BuMgCl, react, albeit slowly, to give the expected products in high yields. In cases where either a Grignard reagent in diethyl ether or a dialkylmagnesium (irrespective of solvent) is used, the major product is the corresponding dimagnesio derivative. A couple of intramolecular transmetallation paths are proposed for these cases. The Cp 2 ZrCl 2 -catalyzed reaction of 1,6-heptadiene with EtMgBr fails to induce the desired bicyclization-ring opening sequence to give the corresponding monocyclic monomagnesium derivatives. On the other hand, the corresponding reaction with n-BuMgBr does proceed as desired to give the monocyclic monomagnesium product which contains a minor amount of the corresponding exo -methylene derivative. Only traces, if any, of the corresponding dimagnesium derivatives reported to be the major products in Et 2 O are formed. This procedure has been applied to catalytically convert several other dienes, i.e., ( E )-1-phenyl-1,6-heptadiene, 2,4,4-trimethyl-1,6-heptadiene, diallyl(benzyl)amine, 1,7-octadiene and 1,2-diallylbenzene, into the corresponding monocyclized compounds in moderate to excellent combined yields.

Stoichiometric reactions of nonconjugated dienes with zirconocene derivatives. Further delineation of the scope of bicyclization and observation of novel multipositional alkene regioisomerization

Abstract The reaction of n-Bu2ZrCp2 with nonconjugated dienes containing substituted vinyl groups can lead to either bicyclization or the formation of conjugated diene-zirconocenes via multipositional regioisomerization.