We demonstrate the platinum mediated diastereoselective ring opening of 2,3-cyclopapanated N-tosylpiperidines never reported so far. This approach yields new precursors to di- and trisubstituted piperidine alkaloids.1,2 We explored the scope and limitations of this chemistry on a newly synthetized cyclopropane library emphasizing on functional group tolerance and the product isomer ratio. This methodology (Scheme A) is compatible with substrates with alkyl, aryl, hydroxyalkyl or alkoxycarbonyl substituents, but alkenes and silyl ethers were found to be unstable under our conditions. The observed selectivity for either the endo- or the exocyclic product was found to be dependent on both the catalyst system and the substrate structure. A new Pt mediated rearrangement was observed with cyclopropanes where the β-hydrogen was absent. Isotope labelling suggested a new Wagner-Meerwein type 1,2 alkyl shift mechanism (Scheme B). These transformations give easy access to natural product like structures promising for piperidine alkaloid total synthesis. References: Bates, R. W.; Kasinathan, S.; Straub, B. F. J. Org. Chem. 2011, 76, 6844. Bates, R. W.; Kasinathan, S. Tetrahedron 2013, 69, 3088.

Platinum-mediated ring opening of 2,3-cyclopropanated N-tosylpiperidines

251st National Meeting (2016)

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