Dienes embedded in quinolizidine and indolizidine structures can be prepared in four steps from cyclic nitrones and bicyclopropylidene. The key intermediates α-spirocyclopropanated N-heterocyclic ketones, generated via a domino 1,3-dipolar cycloaddition/ thermal rearrangement sequence, were converted by Wittig methylenation to the corresponding vinylcyclopropanes (VCPs), which underwent rearrangement to 1,3-dienes in the presence of the Wilkinson Rh(I) complex under microwave heating. The previously unexplored Rh(I)-catalyzed opening of the VCP moiety embedded in an azapolycyclic system occurs at high temperature (110–130 °C) to afford the corresponding 1,3-dienes in moderate yield (34–53%).
Rh-Catalyzed rearrangement of vinylcyclopropane to 1,3-diene units attached to N-heterocycles / F. M. Cordero; C. Vurchio; S. Cicchi; A. de Meijere; A. Brandi. - In: BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1860-5397. - STAMPA. - 7:(2011), pp. 298-303. [10.3762/bjoc.7.39]
Rh-Catalyzed rearrangement of vinylcyclopropane to 1,3-diene units attached to N-heterocycles
CORDERO, FRANCA MARIA;VURCHIO, CAROLINA;CICCHI, STEFANO;BRANDI, ALBERTO
2011
Abstract
Dienes embedded in quinolizidine and indolizidine structures can be prepared in four steps from cyclic nitrones and bicyclopropylidene. The key intermediates α-spirocyclopropanated N-heterocyclic ketones, generated via a domino 1,3-dipolar cycloaddition/ thermal rearrangement sequence, were converted by Wittig methylenation to the corresponding vinylcyclopropanes (VCPs), which underwent rearrangement to 1,3-dienes in the presence of the Wilkinson Rh(I) complex under microwave heating. The previously unexplored Rh(I)-catalyzed opening of the VCP moiety embedded in an azapolycyclic system occurs at high temperature (110–130 °C) to afford the corresponding 1,3-dienes in moderate yield (34–53%).File | Dimensione | Formato | |
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