1033055-85-4Relevant academic research and scientific papers
Alkyne versus allene activation in platinum- and gold-catalyzed cycloisomerization of hydroxylated 1,5-allenynes
Zriba, Riadh,Gandon, Vincent,Aubert, Corinne,Fensterbank, Louis,Malacria, Max
experimental part, p. 1482 - 1491 (2009/04/04)
Chemo- and stereoselective transformations of 3-hydroxy-1,5-allenynes 1 into a variety of new and potentially useful cyclic compounds have been achieved. Substrates bearing a silyl group at the alkyne moiety undergo purely thermal or Lewis acid catalyzed Alder-ene type transformations into 2-methylene-3-vinylcyclopent-3-enol derivatives 2. When heated in the presence of a catalytic amount of PtCl2 or PtCl4, these incipient cyclopentenols could be further transformed into 3-vinylcyclopent-2-enones 3. On the other hand, alkyl-substituted 3-hydroxy-1,5-allenynes proved to be stable under refluxing conditions. Nevertheless, PtCl2 and PtCl4 could selectively activate the alkyne moiety of these substrates toward intramolecular nucleophilic attack of the internal aliene double bond to yield unprecedented 6-methylenebicyclo[3.1.0]hexan-3-one derivatives 4. With gold-based catalysts, provided that the reaction is carried out in dichloromethane, both AuI and AuIII complexes selectively activate the aliene fragment of the substrates toward intramolecular nucleophilic attack of the hydroxyl group to yield 2-ethynyl-3,6-dihydro-2H- pyrans 5. Compounds of type 4 can also be formed with Au1 and Au III complexes if the reaction is carried out in toluene. The reactivity of these new compounds has been partially investigated, and polycyclic ketones were obtained after oxidation under mild conditions or goldcatalyzed cycloisomerization.
