Christophe J. Rousset

Zirconocene-promoted stereoselective bicyclization of 1,6- and 1,7-dienes to produce trans-zirconabicyclo[3.3.0]octanes and cis-zirconabicyclo[4.3.0]nonanes

Abstract The Zr-promoted bicyclization of 1,6- and 1,7-dienes can stereoselectively produce trans-zirconabicyclo[3.3.0]octanes and cis-zirconabicyclo[4.3.0]nonanes, respectively; these compounds can be readily converted into protonolysis, halogenolysis, and carbonylation products.

Novel head-to-tail alkyl-alkene or alkene-alkene coupling via zirconium-catalyzed reaction of alkylmagnesium derivatives with monosubstituted alkenes

Abstract The reaction of monosubstituted alkenes with alkylmagnesium derivatives catalyzed by Cp2ZrCl2 or related zirconocene derivatives provides head-to-tail alkyl-alkene or alkene-alkene coupling products, ∼50% of which are 2,5-dialkyl-4-pentenylmagnesium halides.

Synthesis of cyclopentanol derivatives via palladium-catalyzed cyclic allylmetallation-dehydrometallation

Abstract Treatment of 4-organyl-4-hydroxy-2,7-octadienyl acetate derivatives, i.e., 8 , 10 , 12 , 14 , and 16 with 3 mol % of Pd(PPh 3 ) 4 in refluxing MeCN provides in good yields the corresponding cyclopentanol derivatives, i.e., 9 , 11 , 13 , 15 , and 17 , as mixtures of two diastereomers, the major isomers being those in which the hydroxyl and vinyl groups are cis to each other.

Selective skeletal rearrangement by carbon–carbon bond activation

Skeletal rearrangement of α-substituted organometallic compounds to give β-substituted compounds by carbon-carbon bond activation was performed with bis(η5-cyclopentadienyl)-2,5-dimethyl-zircons- or -hafna-cyclopentane, which were regio- and stereo-selectively converted into the corresponding 3,4-dimethylmetallacyclopentanes in high yield.

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.

Highly regioselective reaction of zirconocene-alkene complexes with aldehydes or ketones

Abstract Reactions of zirconocene-alkene complexes Cp2Zr(CH2CHR)(PR′3) (R  H, Me, Et, SiR″3 or Ar) with aldehydes or ketones were investigated. Zirconocene-ethylene, -propylene or 1-butene complexes reacted with aldehydes or ketones at terminal carbons of alkenes to give the corresponding alcohols after hydrolysis with a high regioselectivity. A similar type of reaction product was also obtained by a reaction of zirconacyclopentanes with aldehydes. This reaction proceeded via β-β′carbon-carbon bond cleavage of zirconacyclopentanes. A reaction of zirconocene-vinylsilane complexes with ketones afforded 3-trimethylsilyl-1-oxa-2-zirconacyclopentanes with an excellent regioselectivity. Carbon—carbon bond formation occurred exclusively at the terminal carbon of vinylsilanes. Their corresponding γ-silylalcohols were obtained after hydrolysis. The products showed that vinylsilanes reacted with carbonyl compounds at the β-carbon to silyl group. It is in sharp contrast to the conventional reactions of vinylsilanes of which the α-carbon normally attacked electrophiles. The reactions of styrene and its derivatives with pentan-3-one on zirconium gave a mixture of two regioisomers. Substituents of alkenes tend to be in α-position to Zr in 1-oxa-2-zirconacyclopentanes. This orientation showed a different aspect of the formation of 1-oxa-2-zirconacyclopentanes from the alkene-alkene coupling reaction on zirconium. The regioselectivity of the reaction with carbonyl compounds decreased in this order; R = alkyl > silyl > aryl.

Enantiomerically pure zirconium and hafnium complexes containing a chiral cyclopentadiene derivative prepared from (−)-β-pinene

Abstract Chirally homogeneous (1 S ,8 R )-3,5,9,9-tetramethyltricyclo[6.1.1.0 2,6 ]deca-2,5-diene 1 has been prepared in five steps and 42% overall yield from (−)-β-pinene; its successive treatment first with n -BuLi and then with ZrCl 4 or HfCl 4 provides, in high yields with high π-facial selectivity, the corresponding dichlorobis { η 5 -(1 S ,8 R )-3,5,9,9-tetramethyltricyclo[6.1.1.0 2,6 ]deca-3,5-dien-2-yl}zirconium or hafnium, respectively.