A simple method for the formation of cyclopropylamines: the first synthesis of tricyclopropylamine

Abstract A mild, one-step method to cyclopropylate amines is described. Treatment of a variety of secondary and primary amines with [(1-ethoxycyclopropyl)oxy]trimethylsilane and sodium cyanoborohydride in methanol gave mono- and dicyclopropylamines in good yield. Sterically hindered di- and tricyclopropylamines, including the previously unreported tricyclopropylamine, were prepared using this method. The pKas of some mono-, di- and tricyclopropylamines were measured showing a reduction of ∼1–2 pKa unit per added cyclopropyl group.