Methylmagnesium tosylate

Friedel-Crafts acylation of 4-bromoindole led to 67, which, after protection by N-tosylation to give 68, was treated with methylmagnesium bromide and afforded compound 66, which contains the welwistatin C3-C16 bond as well as its gem-dimethyl substituent at C(16). A Lewis-acid catalyzed displacement of the tertiary hydroxyl in 66 by a cyclohexanone silyl enol ether afforded intermediate 69, which was then deprotected and N-mclhylalcd to 70 (Scheme 13). 

Several different methods have been employed for the preparation of diazo(trimethylsilyl)meth-ane (1). At present, the best synthetic method seems to be the diazo transfer reaction between diphenylphosphoryl azide and (trimethylsilyl)methylmagnesium chloride.However, the product often contains (chloromethyl)trimethylsilane and hexamethyldisiloxane as impurities. This method can also be employed for the synthesis of diazo(triethylsilyl)methane and diazo(di-ethylmethylsilyl)methane. The diazo transfer reaction can also be carried out with (trimethyl-silyl)methyllithium and tosyl azide. Other methods are the silylation of diazomethane with (trimethylsilyl)trifluoromethanesulfonate or chloro(trimethyl)silane and the base-induced cleavage of A-nitroso-A-[(trimethylsilyl)methyl]urea or the related carbamate or acet-amide.2° =... 

N-N bond formation also occurs when cyclopropylamines are converted to the corresponding cyclopropyl azides by treatment with methyllithium or methylmagnesium bromide ° followed by tosyl azide. The yield can be as high as 50%, but is usually significantly lower ° when methylmagnesium bromide is used. 

Azide synthesis (2, 415). In the definitive paper3 describing the conversion of primary amines into azides by a diazo transfer reaction, methyllithium is preferred to methylmagnesium chloride as the base. The reaction has been extended to hydrazones. Thus, when the hydrazones of benzophenone, fluorenone, and acetophenone are treated with methylmagnesium chloride and then with tosyl azide, the corresponding diazoalkanes are obtained in about 20% yield. 

The Sn2 reaction of propargyl tosylates with trimethylsilyl-methylmagnesium chloride in the presence of a stoichiometric amount of CuCN-2LiCl permits the large-scale synthesis of allenylsilanes (eq 24). ... 

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