Structure of Reactive Intermediates of Organocatalysis

Significance The present work of the Seebach group addresses the isolation and characterization of reactive intermediates in organocatalysis. In this regard, enamine 1 and iminium tetrafluoro­borates 2 - 4 were prepared through conventional methods from 2-phenyl acetaldehyde or cinnamaldehyde, respectively, and the corresponding secondary amine (salt) catalyst. Single crystals of enamine 1 and iminium ions 2 and 3 were subjected to Röntgen structure analysis. The structure of iminium ion 4 was elucidated by 2D NMR spectroscopy. Moreover, the Röntgen and NMR structures were extensively discussed in connection with other, structurally related compounds.