Phosphonium salts reactions with organolithiums

Enolizable A -trimethylsilylaldimines can be generated in situ by the addition of organolithium reagents to bis(trimethylsilyl)formamide. These undergo addition reactions with enolates to form 3-lactams. Phosphonium salts used in catalytic amounts promote the reaction between aryl aldimines and silylketene acetals to form 3-amino esters. Mannich bases with N-2-hydroxyethyl-N-methyl substitution are prepared by the reaction of the iminium salt synthon, 3-methyl-1,3-oxazolidine, with enol silanes in the presence of chloromethylsilanes. ... 

The preparation and immediate reaction of alkyllithium for deprotonation of various acidic compoimds precisely illustrate this aspect (Fig. 34).i 8 representative reaction is the quantitative formation in a few minutes of 2-lithio-1,3-dithiane by sonication of f-butyl chloride, lithium, and 1,3-dithiane in THF. In situ generated butyllithium was used for the deprotonation of alkynes and phosphonium salts. With secondary amines, the strongly basic lithium amides are produced (p. 368). This procedure avoids the use of organolithium auxiliaries with solvent and temperature adjustments. o The isotopically labeled Li hexamethyl disilazide was obtained by this method.i i... 

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