Addressing the asymmetric synthesis of oxindole-based a-amino boronic acids, instead of the expected products we disclosed the efficient homocoupling of oxindole-based N-tert-butanesulfinyl imines, with the generation of chiral, quaternary 1,2-diamines in a mild and completely stereoselective way. The obtained 3,3′-bisoxindoles derivatives were fully characterised by NMR and single-crystal X-ray diffraction analysis and proved to be single diastereoisomers and atropoisomers. A plausible mechanism for the one-pot Cu(II)-catalysed Bpin-addition to the isatin-derived ketimine and subsequent homocoupling is detailed.
Keywords: N-tert-butanesulfinyl ketimine; bis(pinacolato)diboron; 3,3′-bisoxindole; homocoupling; atropoisomer.
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Manenti, M.; Lo Presti, L.; Molteni, G.; Silvani, A. Beilstein Arch. 2022, 20225. doi:10.3762/bxiv.2022.5.v1
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