Alternative Routes for Reductive Alkylations in Liquid Ammonia and Their Selection via Spectroscopic Evidence

Article abstract of DOI:10.1021/ja00290a011

A wide range of unsaturated hydrocarbons have been reduced with alkali metals in liquid ammonia and the carbanionic intermediates detected in situ by NMR and ESR spectroscopy.The substrates cluster into three different groups depending on whether they (i) persist as dianions, (ii) are protonated by ammonia to afford monohydro anions, or (iii) undergo further electron transfer/protonation steps to yield polyhydro derivatives.The alternative modes of behavior can be correctly predicted on the basis of the relevant atom localization energies.The spectroscopic findings are extremely helpful in rationalizing the results of reductive alkylation experiments and in controlling the regioselectivity of novel quenching reactions.