Dimethylphenylsilyl chloride

Dimethylphenylsilyl chloride (lOmmol) was stirred with lithium (30 mmol, Fison s shot ) in THF (25 ml) at -8°C for 36 h. The red solution is stable for several weeks at -20 °C. 

In common with the synthesis of trifluoroisopropenyl-boronic acid, trifluoro-isopropenylsilane can be also prepared in 80% yield by treatment of 2-BrTFP with 1.2 equivalents of magnesium in the presence of 2.0 equivalents of dimethylphenylsilyl chloride in THF at — 10°C to room temperature (Scheme 26.45). This reagent can employ as CF2=C -CH2 synthon, but there have been no reports on the transition metal-catalyzed cross-coupling reaction of tri-fluorinated silane with halides. 

To (E)-stilbcnc oxide (25 mmol) in THF (35 ml) was added freshly prepared dimethylphenylsilyl lithium (25.35 mmol, 1.3 m in THF) dropwise at ambient temperature. The solution was stirred at ambient temperature for 4h, and then poured into saturated ammonium chloride solution (15ml), diluted with ether, and the separated organic layer was dried and concentrated. The crude product (97 3 (Z) (E), g.I.c.) was purified by chromatography on silica gel to give (Z)-stilbene (18.75 mmol, 75%). 

Hydrogen hexachloroplatinate(IV)-Copper(II) chloride, 145 Lithium bis(dimethylphenylsilyl)-cuprate, 161... 

One general method for acyl silane synthesis particularly successful for a-cyclopropyl examples (and even an a-cyclobutyl example) involves treatment of acid chlorides with lithium tetrakis(trimethylsilyl) aluminum or lithium methyl tris(trimethylsilyl) aluminium and cuprous cyanide (vide supra, Section III.A.3)77. For example, cyclopropyl acyl silane (23) was obtained in 89% yield by this process. Improved procedures use lithium t-butyldimethylsilyl cuprate78 and a dimethylphenylsilyl zinc cuprate species79,80 as reagents. 

The low ionic character of the aluminium-silicon bond has been cleverly utilized to develop a very mild, general and effective synthesis of acyl silanes, successful for aliphatic, aromatic, heteroaromatic, a-aUcoxy, a-amino and even a-chiral and a-cyclopropyl acyl sUanes. Acyl chlorides are treated with lithium tetrakis(trimethylsilyl)aluminium or lithium methyl tris(trimethylsilyl) aluminium in the presence of copper(I) cyanide as catalyst to give the acyl silanes in excellent yields after work-up. Later improvements include the use of 2-pyridinethiolesters in place of acyl halides, allowing preparation of acyl silanes in just a few minutes in very high yields indeed (Scheme 9) °, and the use of bis(dimethylphenylsilyl) copper lithium and a dimethylphenylsilyl zinc cuprate species as nucleophiles. 

Dimethylphenylsilyl)-4,4,5,5-tetramethyl-l,3,2-dioxaborolane (1) is prepared by reaction of dimethylphenylsilyllithium with 4,4,5,5-tetramethyl-l,3,2-dioxaborolane (pinacolborane, 2equiv) or 2-isopropoxy-4,4,5,5-tetramethyl-l,3,2-dioxaborolane (2 equiv) (eq 1). Silylboronic esters 2 and 3a are also synthesized via similar routes using methyldiphenylsilyllithium and [(diethyl-ainino)diphenylsilyl]lithium, respectively (eq 2). Diethylamino-substituted silylborane 3a is converted to a chlorine-substituted 4a by reaction with dry hydrogen chloride (eq 3). Silylborane 1 is... 

Bis(silyl)zinc reagents, which are prepared by the reaction of silyllithium with zinc chloride, are also useful and versatile reagents to introduce a silyl group. The copper-catalyzed reaction of bis(dimethylphenylsilyl)zinc with an enantio-enriched allylic benzoate reportedly proceeds in a stereospecific manner to give a chiral allylsilane with high enantiomeric purity (Scheme 3-13). 

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