Claudine Blandy

Synthesis of O-protected azidohydrins catalyzed by titanium and vanadium complexes

Abstract O-protected vicinal azidohydrins are obtained by titanium (or vanadium) complex catalyzed reaction of epoxides on Me 3 SiN 3 via the formation of a transition metal-azide undergoing regio-selective insertion into the oxirane.

The role of early transition metal azides as catalysts of the ring-opening reaction of epoxides with trimethylsilylazide

Abstract Complexes of early transition metals (titanium, vanadium, …) catalyse the reaction of epoxides with Me 3 SiN 3 . When an azido complex is used as precursor, the reaction follows an overall second-order law and the rate constant is proportional to the complex concentration. The regioselectivity (α- or β-cleavage of the ring) is compared to that of the stoichiometric reaction of the transition metal azide with epoxides. It is concluded that the catalytic mechanism involves the intermediary formation of a complex resulting from the nucleophilic attack of the epoxide ring by the N 3 group bonded to the transition metal atom.

Catalytic evidence of the core/shell structure of bimetallic Pd/Rh colloids

The co-reduction of [Rh(C2H4)2Cl]2 and [Pd(η3-C3H5)Cl]2 with vanadocene [Cp2V] in THF, and in presence of poly(vinylpyrrolidone) (PVP), gives bimetallic PVP-protected Rh/Pd colloids. HREM and WAXS experiments show a narrow size distribution centered near 2 nm, indicating the existence of bimetallic particles rather than physical mixtures of monometallic ones. CO chemisorption, followed by IR in CH2Cl2, as well as catalytic hydrogenation of quinoline and phenylacetylene, followed by GC in CH2Cl2 or CH2Cl2/H2O, confirm the presence of core/shell-structured bimetallic colloids, with Pd atoms surrounded by Rh atoms.

Insertion of aldehydes and ketons into a methyltitanium bond. Synthesis and reactivity of alkenoxy derivatives

Abstract The selective insertion of carbonyl groups of aldehydes and ketones such as acetaldehyde or acetone, into the titaniumcarbon bond of the methyl trialkoxy titanium CH 3 Ti(OR) 3 (with R = C 2 H 5 , i-C 3 H 7 , t-C 4 H 9 ) produces mixed tetra-alkoxy titanium complexes. Alkenoxy derivatives are obtained in this way starting from olefinic aldehydes and ketones such as methyl vinyl ketone or acrolein. Alkenoxy derivatives are also obtained by more classical substitution reaction using vinylic alcohol. Their characterization by spectroscopical data and hydrolysis products as well as their reactivity towards AlMe 3 is also described.