Diazo methyllithium

The triazolo-fused 1,2,3,4-tetrazine 494 was obtained in good yield on oxidation of l-amino-5-phenyl-l,2,3-triazolo[4,5-d -, 2,3-triazole 493 with lead tetraacetate (Scheme 258) <1988CC1608>. Fused 1,2,3,4-tetrazines 496 were prepared via reaction of diazocyclopentadienes 495 with methyllithium, followed by a diazo transfer using tosyl azide, as shown in Scheme 259 <1994CB1479, CHEC-III(9.13.9.2.1)730>. 

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° =... 

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. 

Aryl-2//-cyclopenta[e][l,2,3,4]tetrazincs 3 are formed by coupling of the diazocyclopentadi-enes 1 with arenediazonium salts and subsequent reversible electrocyclization of the primary coupling products 2.37 Front the solution of the equilibrium mixture of 2 and 3 the colored tetrazines 3 crystallize. 2-Methyl-277-cyclopenta[e][l,2,3,4]tetrazines 3(R2 = Me) are obtained by addition of methyllithium to 1 followed by a diazo transfer reaction and cyclization.37... 

Homologation Reactions of Ketones. When generated in pentane/THF at — 100°C, diazo(trimethylsilyl)methyllithium reacts with ketones (three examples) and benzaldehyde to give the unstable l-diazo-l-trimethylsilyl-2-alkanols (eq 2) On gentle wanning, the diazo alcohols rapidly lose N2 to give trimethylsilyl epoxides. Since such epoxides readily give aldehydes on treatment... 

Treatment of trimethylsilyldiazoalkanes, obtained by alkylation of diazo(trimethylsilyl)methyllithium with RCH2X, with copper(I) chloride gives excellent yields of ( )-l-trimethylsilyl-alkenes (eq 8). ... 

Preparation of Heterocycles. On reaction with methyl esters, diazo(trimethylsilyl)methyllithium (2 equiv) gives 2-substituted 5-trimethylsilyltetrazoles in 50-90% yield (eq 9). Similarly, reaction with nitriles gives 1,2,3-triazoles in high yield (eq lO). Reaction with (Me3Si)2C=PCl leads to 1,2,4-diazaphospholes (eq ll).i ... 

Reactions with Carbonyl Compounds and Utilization of 2-Diazo-2-(trimethyIsiIyI)ethanoIs. Diazo(trimethylsilyl)-methyllithium (TMSC(Li)N2) reacts with aldehydes and ketones to give lithium 2-diazo-2-(trimethylsilyl)ethoxides by nucleophilic addition, which produce alkylidene carbenes by expulsion of TMSOLi and nitrogen (eq 12). 

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