Silicon‐Directed Nazarov Cyclizations. Part VI. The anomalous cyclization of vinyl dienyl ketones
1988; Wiley; Volume: 71; Issue: 1 Linguagem: Inglês
10.1002/hlca.19880710121
ISSN1522-2675
AutoresScott E. Denmark, Gary A. Hite,
Tópico(s)Oxidative Organic Chemistry Reactions
ResumoAbstract Reactions, of various vinyl dienyl ketones (see la – e , li ) with FeCl, give rise to β,γ‐unsaturated α‐vinyl‐cyclo‐pentenones (see 2a – e , 2i , Table 2 ). The reaction succeeds for vinyl dienyl ketones with substituents on either 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 13 C‐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.
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