Silicon-DirectedNazarov Cyclizations. Part VI. The anomalous cyclization of vinyl dienyl ketones
作者:Scott E. Denmark、Gary A. Hite
DOI:10.1002/hlca.19880710121
日期:1988.2.3
double bond. Aryl dienyl and alkyl dienyl ketones (see 1f–h) do not cyclize cleanly. The effects of substituents on the rate of reaction is discussed in terms of the mechanism of the rearrangement. A 13C-labeling study establishes the pathway as an unusual 1-hydroxypentadienyl-cation electrocyclization to a cyclopentenyl cation which collapses via a pinacol rearrangement to the α-vinyl ketone.
各种乙烯基二烯基酮(见la - e,li)与FeCl的反应会生成β,γ-不饱和α-乙烯基-环戊烯酮(见2a - e,2i,表2)。对于在两个双键上具有取代基的乙烯基二烯基酮,该反应成功。芳基二烯基和烷基二烯基酮(参见1f – h)不能完全环化。根据重排的机理讨论了取代基对反应速率的影响。一项13 C标记研究建立了异常的1-羟基戊二烯基阳离子电环化为环戊烯基阳离子的途径,该环戊烯基通过 频哪醇重排成α-乙烯基酮。