Tandem Reactions Including Aliphatic Claisen Rearrangement

Tandem Reactions Including Aliphatic Claisen Rearrangement 3.1.7.1 Vinylation/Claisen Rearrangement 

A number of vinylation-Claisen rearrangements have been reported as a tandem reaction. Since no additional reagents are required in the thermal Claisen rearrangement, the allyl vinyl ethers can rearrange without isolation. No convenient introduction methods of basically reactive vinyl groups are available for the selective preparation of functionalized vinyl ethers [11,13,14, 22, 24]. 

Fukuyama has found that a one-pot transformation involving vinylation and the Claisen rearrangement was quite effectively performed in n-butyl vinyl ether at reflux temperature [59]. A mixture of aUyUc alcohols, -butyl vinyl ether and catalytic Hg(OAc)2 and NaOAc was stirred at reflux to prepare unsaturated aldehydes (Eq. 3.1.47). 

The reaction of secondary aUylic alcohols bearing trans-l,2-disubstituted olefins proceeded smoothly to furnish the desired aldehydes in good yields (Table 3.1.6, entry 1). Geraniols, which form quartemary carbon centers, rearranged in moderate yield because of low reactivity of vinyl ethers formation. And the one-pot rearrangement of styrene derivatives proceeded in low yield due to preparation of deconjugated products (entries 2—4). 

In developing a general method for preparing 16-ene C,D-ring with natural 

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