Abstract

This paper concerns new possibilities opened by the addition of (mono)organocopper compounds and iodotrimethylsilane (TMSI) to α,β-unsaturated ketones and esters giving the silyl enol ethers and ketene acetals, respectively. We demonstrate the homogeneous addition of methylcopper-tributyl-phosphine-iodotrimethylsilane to methyl cinnamate, the use of organocopper-bromotrimethylsilane combinations, the dominating formation of Z-silyl enol ethers on conjugate addition of methyl- and butylcopper/TMSI to benzalacetone, and the formation of silyl enol ethers in other additions of organocopper compounds and TMSX to conjugated ketones. The Z-selectivity for addition to benzalacetone corresponds to s-cis conformations in π-complexes between copper (I) chloride and 1-penten-3-one or 3-buten-2-one. The stereoselectivity could support a reaction path via π-complexes between organocopper-iodotri-methylsilane complexes and s-cis conformers of the substrates.

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