ORGN 361

Several authors have observed that lithiated nitriles react with enones to yield larger amounts of 1,4-adducts than do other lithium reagents (e.g. dithianyllithium). These results have been rationalized using extended transition states (1), differing reactivities of monomers (2) and dimmers (3) or hard-soft-acid-base theory. These explanations are valid only if the reactions are under kinetic control. Our investigation of the addition of lithiophenylacetonitrile to benzylidene acetone finds that both 1,2 and 1,4 additions are reversible processes as shown by diastereomer interconversions, trapping and cross-over experiments. Using rates of these processes, an approximate energy diagram can be determined.