Controlled formation of tetramethylammonium mono- and diylide

The reaction of tetramethylammonium bromide with n-butyllithium can selectively yield either trimethylammonium methylide or lithium dimethylammonium dimethylide, depending on the reaction conditions, as shown by 13C-NMR analysis of the deuterium-labelled species resulting from acidic trapping with DCl. So a simple synthesis of mono- or twice-functionalised methylammonium salts is allowed from a very usual starting material.