Tetrahydrofuran → Dimethyl titanocene

Participants

Reaction Conditions

Reaction Steps

To a well stirred slurry of titanocene dichloride (CP2TiCl2) (249 g, 1.00 mol) in toluene (2.75 L) chilled to −5° C. (internal temp) was added methyl magnesium chloride (CH3MgCl) (750 mL, 3.0M in THF, 2.25 mol) over 1 h, maintaining the temperature below 8° C. The resulting orange slurry is aged at 0-5° C. for 1 h, or until the insoluble purple Cp2TiCl2 has dissolved. A NMR was taken to confirm reaction completion (see below), then the reaction was quenched into a solution of 6% aqueous ammonium chloride (700 mL), maintained at 0-5° C. The layers were separated and the organic phase was washed with cold water (3×575 mL) and brine (575 mL), then was dried with Na2SO4 (220 g). The filtered organic layer was evaporated to 1.5 Kg (maintaining an internal temperature of 25° or less). Weight % assay by 1H NMR showed the solution to contain 187 g product (90%, 12.5 wt % solution in toluene/THF). Typically, the material was greater than 95% pure, with only traces of the starting material and monomethyl intermediate. The solution may be further concentrated to 1.0 Kg, giving a 18 wt % solution in toluene, allowing for an easier assay. However, the presence of a small amount of THF increases the stability of the compound. The material was stored under nitrogen in a sealed carboy at 0° C. 1H NMR Cp2Ti(CH3)2: δ 6.05 (s, 10H), −0.05 (s, 6H). Cp2TiCl(CH3): δ 6.22 (s, 10H), 0.80 (s, 3H). Cp2TiCl2: δ 6.56 (s, 10H). 13C NMR Cp2Ti(CH3)2: δ 113.20 (Cp2), 45.77 ((CH3)2). Cp2TiClCH3: δ 115.86 (Cp2), 50.37 (CH3). Cp2TiCl2: δ 120.18.

Provenance & Evidence