Functionalized alkylidenecyclopentenes by acid-catalyzed electrocyclic ring closure of (2Z)-(di)vinylallene acetals
摘要:
Acid-induced electrocyclic ring-closure of (2Z)-4-tert-butyl-3-methyl-2,4,5,7-tetraene acetals 3 afforded a mixture of alkylidenecyclopentene dioxanes Z-4 and E-4. The lack of torquoselective effects on the electrocyclization suggested the transition state structures for the two alternative conrotatory modes to have similar energies. The results of an ab initio study of a model system at the DFT B3LYP/6-31G* level were consistent with this hypothesis. (C) 1997 Elsevier Science Ltd.
Functionalized alkylidenecyclopentenes by acid-catalyzed electrocyclic ring closure of (2Z)-(di)vinylallene acetals
作者:Angel R. de Lera、José García Rey、David Hrovat、Beatriz Iglesias、Susana López
DOI:10.1016/s0040-4039(97)01747-4
日期:1997.10
Acid-induced electrocyclic ring-closure of (2Z)-4-tert-butyl-3-methyl-2,4,5,7-tetraene acetals 3 afforded a mixture of alkylidenecyclopentene dioxanes Z-4 and E-4. The lack of torquoselective effects on the electrocyclization suggested the transition state structures for the two alternative conrotatory modes to have similar energies. The results of an ab initio study of a model system at the DFT B3LYP/6-31G* level were consistent with this hypothesis. (C) 1997 Elsevier Science Ltd.
Torquoselectivity in the Cationic Cyclopentannelation of (2Z)-Hexa-2,4,5-trienal Acetals
作者:Beatriz Iglesias、Angel R. de Lera、Jesús Rodríguez-Otero、Susana López
calculations for model systems are consistent with the acid-catalyzed rearrangement of 2-[(1Z)-hexa-1,3,4-trienyl]dioxolanes 1 to tetrahydroalkylidenecyclopenta-1,4-dioxins 4; this involves the electrocyclic ringclosure of substituted hydroxypentadienyl carbocations. The reaction, which may be considered a variant of the Nazarov cyclization, occurs much more readily than the standard Nazarov cyclization, proceeding