Organocatalysis of CN/CN and CC/CN Exchange in Dynamic Covalent Chemistry

The reversibly formed C?N bond plays a very important role in dynamic covalent chemistry and the C?N/C?N exchange of components between different imine constituents to create dynamic covalent libraries has been extensively used. To facilitate diversity generation, we have investigated an organocatalyzed approach, using L ‐proline as catalyst, to accelerate the formation of dynamic libraries of [n×n] imine components. The organocatalysis methodology has also been extended, under somewhat modified conditions, to reversible C?C/C?N exchange processes between Knoevenagel derivatives of barbituric acid and imines, allowing for the generation of increased diversity.     

α-Fluoroacrylonitriles: Horner-Wittig synthesis and conversion into 2-fluoroallylamines and C-(1-fluorovinyl)nitrones

α-Fluoroacrylonitriles 2 were synthesized in moderate to good yields by Horner-Wittig (HW) reaction of aldehydes and ketones with (diphenylphosphinoyl)fluoroacetonitrile (1), prepared in situ from commercially available fluoroacetonitrile and diphenylphosphinyl chloride. New synthetic applications of 2 are presented with the one-pot conversion into 2-fluoroallylamines 6 and C-(1-fluorovinyl)nitrones 8 through a diisobutylaluminum hydride (DIBALH)-reduction transimination protocol. The scope and limitations of this procedure are discussed.