Catalytic Carboalumination of Olefins with Cyclopentadienylamidotitanium Dichloride Complexes
摘要:
The half-sandwich metallocene eta(5)-(C5Me4)SiMe2N(tBu)TiCl2 reacts with a stoichiometric amount of dibutylmagnesium in tetrahydrofuran to form a robust monobutyl monochloride eta(5)-(C5Me4)SiMe2N(tBu)Ti(Bu)Cl. X-ray crystallography reveals an undistorted eta(1)-butyl ligand. In the presence of an excess of triethylaluminum the dichloride eta(5)-(C5Me4)SiMe2N(tBu)TiCl2 serves as a catalyst for the carboalumination of olefins. The organometallic products of these reactions can be oxidized to 1,4-butanediols. The enantioselective carboalumination of allylbenzene by the chiral complex eta(5)-(Ind)SiMe2N[CH(Me)Ph]TiCl2, derived from (-)alpha-methylbenzylamine, affords 2-benzyl-1,4-butanediol in 53% yield and 28% enantiomeric excess.