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Regioselective and diastereoselective borono-Mannich reactions with pinacol allenylboronate.

Research paper by Thanaphat T Thaima, Stephen G SG Pyne

Indexed on: 06 Feb '15Published on: 06 Feb '15Published in: Organic Letters



Abstract

The first documented study of the borono-Mannich (Petasis) reactions of pinacol allenylboronate is described. The reactions of salicylaldehyde and primary and secondary amines are highly regioselective and give homopropargylamine and α-allenylamine products, respectively. In contrast, glycoaldehyde and chiral α-hydroxyaldehydes give exclusively anti-β-amino-β-allenyl alcohol products, irrespective of the nature of the amine component. These reactions are highly regio- and diastereoselective and can be employed using an enantiomerically enriched α-hydroxyaldehyde without detectable racemization.