Lithium (trimethylsilyl)diazomethane

The Uses of Lithium (trimethylsilyl)diazomethane

When generated in pentane/THF at ?100°C, diazo(trimethylsilyl)methyllithium reacts with ketones (three examples) and benzaldehyde to give the unstable 1-diazo-1-trimethylsilyl-2-alkanols (eq 2).On gentle warming, the diazo alcohols rapidly lose N2 to give trimethylsilyl epoxides. Since such epoxides readily give aldehydes on treatment with acid, the method represents an overall homologation of a ketone to the next higher aldehyde.
When diaryl ketones are used, diarylalkynes are formed in good yield (eq 3).The reaction presumably proceeds via the diazoalkene followed by aryl migration with loss of nitrogen.

Preparation

prepared in situ by lithiation of trimethylsilyldiazomethane using n-butyllithium; prepared in situ by lithiation of trimethylsilyldiazomethane (TMSCHN2) using butyllithium, lithium diisopopylamide (LDA), or lithium 2,2,6,6-tetramethylpiperidide (LTMP). The lithium salt is easily converted to the corresponding magnesium bromide salt (eq 1).