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Organoborane derivatives provide some of the most versatile and useful intermediates in synthetic and medicinal chemistry. In 2006, Nozaki, Yamashita and co-workers provided a breakthrough in organoelement synthesis via the... [ view full abstract ]

Organoborane derivatives provide some of the most versatile and useful intermediates in synthetic and medicinal chemistry. In 2006, Nozaki, Yamashita and co-workers provided a breakthrough in organoelement synthesis via the realisation of the first nucleophilic boryllithium reagents Li{B(NArCH)₂}(THF)₂ (Ar = 2,6-(i-Pr)₂C₆H₃).¹ This new source of nucleophilic boryl anions opens the route to new syntheses of organoboranes but involves the use of highly reducing reaction conditions. 

In this contribution, we present the simple synthesis of a new magnesium boryl species [HC{(Me)CN(2,6-ⁱPr₂C₆H₃)}₂Mg{pinB(BpinnBu)}] through the heterolytic activation of the B-B bond of bis(pinacolato)diboron. The displacement of the BuBpin by a strongly coordinating base such as 4-dimethylaminopyridine (DMAP) leads to the formation of a terminal magnesium boryl [HC{(Me)CN(2,6-ⁱPr₂C₆H₃)}₂Mg(DMAP){Bpin}]. This new magnesium boryl can act as an unambiguous nucleophile through its reactions with alkyl halides, ketones and carbodiimides.² It could also be used in the synthesis of new unsymmetrical diboranes via the reaction with boron sources to lead to the formation of “pinB-BR₂”.

References

¹ Y. Segawa, M. Yamashita, K. Nozaki, Science, 2006, 314, 113

² A.-F. Pécharman, A. L. Colebatch, M. S. Hill, C. L. McMullin, M. F. Mahon, C. Weetman, Nat. Commun., in press