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You are using Science Of Synthesis as a Guest. Please login or sign up for a free trial to access the full content. Variation 3: Reaction of Carbonyl Compounds with Dimetal Species Derived from (Dibromomethyl)(trimethyl)silane

DOI: 10.1055/sos-SD-004-00770

Oshima, K.Science of Synthesis, (20024727.

Several gem-dimetal compounds, such as dimagnesium and dizinc, have been prepared from (dibromomethyl)trimethylsilane upon treatment with magnesium or a zinccopper couple,[‌34‌] respectively. A more facile preparative method for [bis(bromozincio)methyl]trimethylsilane or dichromium species has been developed. Thus, treatment of (dibromomethyl)trimethylsilane (61) with chromium(II) chloride in dimethylformamide gives the gem-dichromium reagent. The addition of aldehydes to this dimetal species provides E-alkenylsilanes exclusively (Scheme 21).[‌35‌] However, a one-pot transformation of aldehydes to E-alkenylsilanes using triiodomethane, manganese metal, chlorotrimethylsilane, and a catalytic amount of chromium(II) chloride has been reported.[‌36‌] Esters (e.g., 64) are converted into β-alkoxy-substituted alkenylsilanes such as 65 by means of the reagent prepared from (dibromomethyl)trimethylsilane, zinc, titanium(IV) chloride and N,N,N,N-tetramethylethylenediamine.[‌37‌] Titanium(II) chloride mediated reaction of [bis(bromozincio)methyl]trimethylsilane with aldehydes also provides the corresponding alkenylsilanes, but with lower stereoselectivity.[‌38‌] The synthesis of 1,1-disilyl-substituted alkenes (e.g., 67) from aldehydes and dibromobis(trimethylsilyl)methane (66) using chromium(II) chloride in dimethylformamide has been reported.[‌39‌]

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