Ketones torquoselective olefination

The ( )-p-alkoxy divinyl ketones 129, potential Nazarov reaction precursors, are prepared according to the torquoselective olefination methodology with ynolates (Fig. 45). For example, ethyl 3-phenylpropionate (127) is olefinated by the ynolate to afford the p-alkoxy-ot,p-unsaturated acid 128 with high -selectivity. The acid 128 is converted into the Weinreb amide, which is subjected to alkenylation to provide the p-alkoxy divinyl ketone 129 in good overall yield. 

In contrast, the C-C triple bond shows excellent effect on torquoselectivity. Alkynyl aUcyl ketones 81 are olefinated by ynolates to afford the tetrasubstituted olefins 83 in good -selectivity (Fig. 28) [72]. In the electrocyclic reaction of 82, the alkynyl group prefers outward rather than inward rotation over the alkyl and alkenyl... 

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