n-Butyllithium-Induced Tandem [3,3]-Sigmatropic Rearrangement and Carbonyl Olefination of Allyl-1,1-dichlorovinyl Ethers.

Exposure of dichlorovinyl ethers 1 to n-butyllithium and addition of saturated or unsaturated aldehydes, ketones, or esters at ambient temperature furnishes rearranged α,β-unsaturated carboxylic acids, isolated as their corresponding methyl esters 2 in 48-91% overall yields. Exposure of dichlorovinyl ethers 1 to n-butyllithium, addition of aldehydes, ketones, dialdehydes, or diketones at -78 °C, and warming to 80 °C in the presence of SiO2 provide 1,4-dienes 3 or cycloalken-1-ols (or their dehydration products) 4 in 45-72% overall yields.