Direct preparation and structure determination of tertiary and secondary amine boranes from primary or secondary amine boranes

New secondary and tertiary amine borane derivatives were prepared in a one-pot reaction starting from primary amine boranes. The reaction involves treatment of an amine borane with 2 equivalents of s-BuLi at −78 °C. In general, mixtures of mono and di metallated products were obtained. Alkyl iodides and benzyl chloride reacted with the lithiated amine, but aldehydes and ketones were reduced. Conversion was high as determined by NMR, but moderate to low yields were obtained after chromatography, possibly due to decomposition on silica. Crystal structures were obtained for the compounds 3a, 3b and 3c.

Graphical abstractA series of novel secondary and tertiary amine boranes derivatives have been synthesized in a one-pot reaction and structurally characterized (solution 1H, 13C and 11B NMR spectroscopy; three crystal analyses). The synthesis was done according to the following reaction.Figure optionsDownload full-size imageDownload as PowerPoint slide