Acyclic enolates acid catalysis

Some electron-rich olefins, such as enol ethers 170, react directly with 32 under mild conditions with Lewis acid catalysis. The first product of the reaction results from addition of the S-Cl bond to the olefin, the sulfur atom being attached to the carbon / to the oxygen and the chlorine in the a-position. If the / -carbon carries a hydrogen atom, elimination of HCl can be effected with mild bases such as triethylamine to regenerate a double bond. The reaction works with both cyclic and acyclic enol ethers, the latter case giving ( ) (Z)-mrxtures of products 171 (Equation 13) <2000JHC583>. 

Trimethylsilyl enol ethers of acyclic and alicyclic ketones add to a)S-unsaturated nitroalkanes in Michael fashion under Lewis acid catalysis. Direct hydrolysis of the crude product leads to good yields of 1,4-diones.The ease of access to the starting materials, the high regioselectivity of the addition (the reaction conditions do not cause migration of the double bond in the enol ether), and the simplicity of the manipulations involved underline the usefulness of the method (Scheme 15, p. 83). 

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