Allylic stannyl ethers rearrangement

The importance of the base used in the [2,3]-Wittig reaction is made clear by the work of Mitchell and coworkers who have reported the rearrangements of silyl- and stannyl-substituted diallyl ethers. They found that the use of LDA on such substrates (38, 41, 43) leads to [2,3]-Wittig reaction while employing lithium diethylamide can result in an allyl-vinyl ether rearrangement instead. 

Transmetallation can be employed in order to avoid the use of strongly basic conditions. One such variant is the [2,3]-Wittig-Still rearrangement wherein stannyl ethers can be converted to homoallylic alcohols. Several examples of this tranformation in the synthesis of amino acid components of bioactive polyoxins have been reported by Ghosh. In their synthesis of 5-0-carbomylpolyoxamic acid, a bioactive amino acid nucleoside, E and Z-allylic stannyl ethers, such as 45, derived from an isopropylidene L-threitol derivative, were subjected to the [2,3]-Wittig-Still rearrangement. 

Sigmatropic rearrangements. The Claisen rearrangement of allyl vinyl ethers is promoted by i-BUjAl. Furthermore, the carbonyl group of the products also undergoes reduction to furnish 4-alkenoIs. A stannyl group is lost in the products of distannyl- and silylstannyl-substituted allyl vinyl ethers when the rearrangement is conducted in the presence of i-BUjAL... 

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