RESUMEN
By using rapid injection NMR, it has now been possible to prepare and characterize the η(3) 'π-allyl' copper(III) intermediate that has been proposed for addition reactions of organocopper(I) reagents and α,ß-unsaturated carbonyl compounds.
RESUMEN
They "know" where to go: a powerful orientation effect has been observed in complexes of mixed organocuprates [R(T)R(NT)CuLi] and substrates with C-C, C-N, and C-S double bonds (see scheme; Th=thienyl). The preferred geometry of the intermediate complex sets up the facile addition of R(T) to the double bond, rather than addition of the "dummy ligand", R(NT) .
RESUMEN
Upon rapid injection, a variety of thiocarbonyl compounds react with the Gilman reagent Me(2)CuLi at -100 degrees C inside the probe of an NMR spectrometer to give high yields of complexes. Typical examples of substrates include carbon disulfide, methyl dithioacetate, methyl dithiobenzoate, thiobenzophenone, ethylene trithiocarbonate, and phenyl isothiocyanate. Evidence suggesting the formal oxidation state of copper in these complexes to be Cu(III) is presented. The last example was particularly interesting, since it involved a transient intermediate that was identified as a complex with a C-N double bond. Methyl isothiocyanate gave a stable C-N double-bond complex.