Methyl Trichlorosilyl Ketene Acetal1

[4519-10-2] C3H5Cl3O2Si (MW 207.52) InChI = 1S/C3H5Cl3O2Si/c1-3(7-2)8-9(4,5)6/h1H2,2H3 InChIKey = LMVJWNCKICXPHV-UHFFFAOYSA-N (reagent for the enantioselective acetate aldol additions to aldehydes1 and ketones2) Physical Data: bp 25 °C (5 mmHg), d20 = 1.3144 g dm−3 Solubility: soluble in halogenated organic solvents such as methylene chloride, chloroform, carbon tetrachloride; sparingly soluble in hydrocarbon and ethereal solvents. Analysis of Reagent Purity: 1H NMR and elemental analysis. Preparative Methods: two different routes have been developed for the preparation of methyl trichlorosilyl ketene acetal. One route is through bis(tributyltin) oxide-catalyzed transmetalation of methyl tributylstannyl acetate 2 with silicon tetrachloride (eq 1).3 When the reaction is complete, excess silicon tetrachloride is removed and the product is purified by fractional distillation under reduced pressure. (1) Alternatively, methyl trimethylsilylacetate 3 can be converted to 1 cleanly when trichlorosilyl triflate is used (eq 2).3 This route has the advantage of not using toxic tin compounds. However, due to the similar boiling point, a complete removal of trimethylsilyl trifluoromethanesulfonate by-product 4 from 1 by fractional distillation is difficult. This method is therefore suitable only for use when 4 does not interfere with the subsequent reaction of 1. (2) Handling, Storage, and Precautions: methyl trichlorosilyl ketene acetal is a thermally unstable and hydrolytically labile compound, which is best used immediately after its preparation. The thermal rearrangement to the C-silyl isomer occurs rapidly at 70 °C4 and proceeds steadily albeit slowly at room temperature. If its storage is unavoidable, it must be kept at the lowest possible temperature. Its hydrolytic decomposition is instantaneous and anhydrous conditions are required for all the manipulations. This reagent is volatile and corrosive. Good ventilation and personal protection equipment are required for its handling.