Lithium napthalenide

The /3-position of an enamine system is much more difficult to meta-late than the a-position because of the higher electron density on the /3-carbon, and so additional activation, or stronger base systems, are often required for efficient reaction. Thus, successful /3-lithiation of the 3-(phenylthio)enamine of morpholine can be achieved because of the stabilizing effect of the sulfur atom, whereas reductive lithiation of the same species can be achieved with lithium napthalenide or lithium in liquid ammonia (Scheme 131) [82JCR(M)621,82JCR(S)48]. Similar /3-lithioenam-... 

Although the choice of phosphine ligand was found to be crucial for the formation and subsequent reactivity of the organocopper species, the presence of malodorous phosphine ligands was often found to interfere with product isolation. In our search for a more reactive copper that did not require the use of phosphorus ligands, we discovered that the lithium napthalenide reduction of a solution of a commercially available lithium 2-thienylcyanocuprate or CuCN LiCl complex produced a highly reactive zerovalent copper complex. 

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