Post‐Assembly Reactivity of N‐Aryl Iminoboronates: Reversible Radical Coupling and Unusual B−N Dynamic Covalent Chemistry. Issue 46 (25th July 2018)

• Record Type: Journal Article
• Authors: Keyzer, Evan N.; Sava, Alexandru; Ronson, Tanya K.; Nitschke, Jonathan R.; McConnell, Anna J.
• Is Part Of: Chemistry. Volume 24:Issue 46(2018)
• Page Start: 12000
• Page End: 12005
• Publication Date: 2018-07-25
• Subjects: dynamic covalent chemistry -- iminoboronate -- post-assembly -- radical coupling -- supramolecular chemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201802790
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Post‐assembly reaction of a dynamic covalent iminoboronate system following addition of Cp2 Co resulted in the formation of a series of new reductively coupled dianionic dimers via C−C bond formation. The dimers formed as a mixture of BN‐containing isomeric products: diastereomers rac 5 and meso 5, with coupled five‐membered rings, and enantiomeric rac 6, with a fused six‐membered ring bicyclic system from C−C bond formation and rearrangement of the B−N bonds. Each isomer was identified using 1 H NMR spectroscopy in combination with single crystal X‐ray structure determination. Interestingly, interconversion between the coupled five‐membered rings ( rac 5 ) and fused bicyclic systems ( rac 6 ) was found to occur through an unprecedented breaking and reforming of the B−N covalent bond. Further, the coupled products could be converted quantitatively back to their iminoboronate precursors with addition of the electron abstractor Ph3 C + . Abstract : Très B−N ensemble ! The reversible reductive coupling of iminoboronates gave not only the expected rac and meso diastereomeric products, but also a third product from the unusual rearrangement of the B−N covalent bonds. Interconversion between the rac isomers was observed but not between the meso and rac products.