Imine, boronate assemblies

Jamison has reported the unprecedented nickel-catalyzed assembly of allylic amines 156 from three simple starting materials alkynes, imines, and trialkylbor-anes or boronic acids. The participation of boronic acids in this methodology greatly enhances its synthetic potential, owing to their greater availability (Scheme 8.68) [145]. An asymmetric version of the reaction has also been developed but gave only moderate enantiomeric excesses (33 to 42%). 

In comparison to abundant examples of noncovalent supramolecular assemblies,relatively few structures have been built with strong covalent bonds. This is due to the fact that normal covalent bonds are not easily broken and reformed. One can manipulate the temperature and conditions so that the formation of stable imines, esters, disulfides, hydrazones, and boronate esters is reversible. Some examples of these covalent self-assembled systems include disulfide hosts and covalent organic frameworks. ... 

FIGURE 11. The synthesis of dendrimers based on a coordinatively assembled pyridine-boronate ester macrocyles combine ester formation, B-N interaction, and imine formation in one step. 

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