- A substrate-based approach to skeletal diversity from dicobalt hexacarbonyl (C1)-alkynyl glycals by exploiting its combined ferrier-nicholas reactivity
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Novel substrates that combine dicobalt hexacarbonyl propargyl (Nicholas) and pyranose-derived allylic (Ferrier) cations have been generated by treatment of hexacarbonyldicobalt (C-1)-alkynyl glycals with BF3 .Et2O. The study of these cations has resulted in the discovery of novel reaction pathways that have shown to be associated to the nature of O-6 substituent in the starting alkynyl glycals. Accordingly, compounds resulting from ring expansion (oxepanes), ring contraction (tetrahydrofurans), or branched pyranoses, by incorporation of nucleophiles, can be obtained from 6-O-benzyl, 6-hydroxy, or 6-O-silyl derivatives, respectively. The use of a 6-O-allyl alkynyl glycal led to a suitable funtionalized oxepane able to experience an intramolecular Pauson-Khand cyclization leading to a single tricyclic derivative.
- Lobo, Fernando,Gomez, Ana M.,Miranda, Silvia,Lopez, J. Cristobal
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p. 10492 - 10502
(2014/08/18)
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- Formation and reactivity of new Nicholas-Ferrier pyranosidic cations: Novel access to oxepanes via a 1,6-hydride shift/cyclization sequence
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Pyranosidic allylic (Ferrier) cations that share dicobalt hexacarbonyl propargyl (Nicholas) stabilization at C-1 display a remarkable reactivity leading to either substituted oxepanes or 3-C-branched pyranosides, depending on the substituent at O-6.
- Gomez, Ana M.,Lobo, Fernando,Perez De Las Vacas, Daniel,Valverde, Serafin,Lopez, J. Cristobal
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supporting information; experimental part
p. 6159 - 6161
(2010/11/02)
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