2024-03-28T23:09:23Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1033502016-02-18T00:29:50Zcom_10261_33com_10261_5col_10261_286
00925njm 22002777a 4500
dc
Montserrat, Sergi
author
Faustino, Helio
author
Lledós, Agustí
author
Mascareñas, José L.
author
López, Fernando
author
Ujaque, Gregori
author
2013
The mechanism of the gold-catalyzed intermolecular cycloaddition between allenamides and 1,3-dienes has been explored by means of a combined experimental and computational approach. The formation of the major [4+2] cycloaddition products can be explained by invoking different pathways, the preferred ones being determined by the nature of the diene (electron neutral vs. electron rich) and the type of the gold catalyst (AuCl vs. [IPrAu]+, IPr=1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene). Therefore, in reactions catalyzed by AuCl, electron-neutral dienes favor a concerted [4+3] cycloaddition followed by a ring contraction event, whereas electron-rich dienes prefer a stepwise cationic pathway to give the same type of formal [4+2] products. On the other hand, the theoretical data suggest that by using a cationic gold catalyst, such as [IPrAuCl]/AgSbF6, the mechanism involves a direct [4+2] cycloaddition between the diene and the gold-activated allenamide. The theoretical data are also consistent with the observed regioselectivity as well as with the high selectivity towards the formation of the enamide products with a Z configuration. Finally, our data also explain the formation of the minor [2+2] products that are obtained in certain cases. The mechanism of the gold-catalyzed intermolecular cycloaddition between allenamides and 1,3-dienes has been explored by a combined experimental and computational approach. The formation of the major [4+2] cycloaddition products can be explained by invoking different pathways, the preferred ones being determined by the nature of the diene (electron neutral vs. electron rich) and the type of gold catalyst (AuCl vs. [IPrAu]+, IPr=1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene, see scheme).
Chemistry - A European Journal 19: 15248-5260 (2013)
http://hdl.handle.net/10261/103350
10.1002/chem.201302330
Cycloaddition
Density functional calculations
Gold Reaction mechanisms
Allenamides
Mechanistic intricacies of gold-catalyzed intermolecular cycloadditions between allenamides and dienes