IODOTRIMETHYLSILANE-PROMOTED ADDITIONS OF MONOORGANOCOPPER COMPOUNDS TO ALPHA,BETA-UNSATURATED KETONES, ESTERS, AND LACTONES

Conjugate additions with the efficient monoorganocopper-iodotrimethyls ilane combination, exemplified plified mainly with methylcopper, butyl copper, and tert-butylcopper, proceed cleanly, smoothly, and rapidly t o a variety of alpha,beta-unsaturated carbonyl compounds; cyclic and a cyclic enones, beta-alkoxy enones, enoates and lactones in ether, THF, and dichloromethane, often at -78-degrees-C. The RCu-(LiI)-TMSI reage nt gives a good economy of group transfer with good to excellent yield s of conjugate adducts. Lithium iodide, present from preparation of th e organocopper compounds, increases the rate of the reactions and is a favorable component. Additions are faster, but somewhat less selectiv e, in THF than in ether. Careful workup after addition of triethylamin e or pyridine at low temperature permits isolation of TMS enol ethers and TMS ketene acetals. Acyclic enones preferentially give the Z-silyl enol ethers. The RCu(LiI)-TMSI system is a most useful alternative to the conventional lithium diorganocuprates in conjugate additions.