Trimethylsilyl methylmagnesium bromide

Diazo compounds have also been used as precursors in the preparation of pyrazoles and indazoles. The copper-promoted cycloaddition reaction of lithium acetylides 18 with diazocarbonyl compounds 19 provided a direct and efficient approach to the synthesis of pyrazoles 20 <07AG(I)3242>. A facile, efficient, and general method for the synthesis of 1-arylated indazoles 22 and A-unsubstituted indazoles 23 by the 1,3-dipolar cycloaddition of benzynes, generated from 21, with diazomethane derivatives has been reported <07AG(I)3323>. Reaction of diazo(trimethylsilyl)methylmagnesium bromide with aldehydes or ketones gave 2-diazo-2-(trimethylsilyl)ethanols, which were applied to the synthesis of di- and trisubstituted pyrazoles via [3+2] cycloaddition reaction with ethyl propiolate or dimethyl acetylenedicarboxylate <07S3371>. 

Diazo-2-(trimethylsilyl)ethanols can be almost quantitatively obtained from carbonyl compounds by the reaction with diazo-(trimethylsilyl)methylmagnesium bromide (TMSC(MgBr)N2)... 

The reaction of l,4-bis(trimethylsilyl)-l,3-butadiyne (174) with disilanes, followed by treatment with methylmagnesium bromide, produces i,l,4,4-tetra(-trimethylsilyl)-l,2,3-butatriene (175) as a major product[96]. The reaction of octaethyltetrasilylane (176) with DMAD proceeds by ring insertion to give the six-membered ring compounds 177 and 178[97], The l-sila-4-stannacyclohexa-2,5-diene 181 was obtained by a two-step reaction of two alkynes with the disilanylstannane 179 via the l-sila-2-stannacyclobutane 180[98],... 

A 3 M diethyl ether solution of methylmagnesium bromide is added dropwise to a stirred solution of the tris-(trimethylsilyl) derivative of 15-oxo-PGF2a in diethyl ether at 25°C. 

The reaction of the silicon-carbon double-bonded intermediate generated from phenylpentamethyldisilane with methyllithium and with methylmagnesium bromide leads to the formation of wholly unexpected products (92). Thus, irradiation of 34 in the presence of methyllithium with a low-pressure mercury lamp in diethyl ether followed by hydrolysis produces l,3-bis(trimethylsilyl)benzene (42) and 1,2-bis(trimethylsilyl)-benzene (43) in 60 and 20% yield, respectively, in addition to an 8% yield of phenyltrimethylsilane (Scheme 13). Surprisingly, no disilyl-substituted cyclohexadienes that might be expected from addition of methyllithium to the intermediate followed by hydrolysis are observed. In this photolysis,... 

Carbometalation of silylalkynes. In the presence of this nickel-aluminum catalyst, methylmagnesium bromide adds to 1-trimethylsilyI-l-octyne (1) to give the cis-addition product 2, which isomerizes slowly to 3, The use of ethylmagnesium bromide results in reduction mainly to cis-1 -trimethylsilyl-1 -octene. The products 2 and 3, as expected, react with a variety of electrophiles to give di- and trisubstituted... 

Preparative Methods (1) reaction of 2,3-dibromopropene with lithium (trimethylsilyl)cuprate in HMPA at 0°C (63-90%) (2) reaction of 2,3-dibromopropene with tri-chlorosilane in the presence of trichlorosilane and cop-per(l) chloride, followed by treatment with methylmagnesium bromide (63-71%).i 3- ... 

Preparative Method the best procedure for the preparation of trimethylsilylacetone is the reaction of trimethylsilyl-methylmagnesium chloride or bromide with acetic anhydride. Other useful preparative methods for a-trimethylsilyl ketones involve the reaction of trimethylsilylmethylmagnesium chloride with acid chlorides, or with aldehydes followed by oxidation of the resulting /3-hydroxysilane to the ketone. When the trialkylsilyl group is very large, particularly the triisopropylsilyl group, a rearrangement from the silyl enol ether to the a-silyl ketone is possible. ... 

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