Propargyl Chlorides as Sources for Cobalt Stabilized γ-Carbonyl Cations

Article abstract of DOI:10.1021/jo00128a022

Hexacarbonyldicobalt complexes of γ-chloroalkynones and γ-chloroalkynoates (5) were found to undergo silver-mediated Nicholas condensation reactions with silyl enol ethers or silyl ketene acetals (10) to give 1,6-dicarbonyl complexes 11 in fair to good yields.Substrates 5 with γ-alkyl substitution formed diastereomeric products with enol silanes 10a and 10b.Reactions with propiophenone trimethylsilyl enol ether (10b) gave good levels of syn diastereoselection, whereas reactions with cyclohexanone trimethylsilyl enol ether (10a) were only slightly diastereoselective, favoring the anti diastereomer.When conducted in acetonitrile, the silver-mediated reaction of 5e gave a radical dimerization product 13, isolated as the syn diastereomer.