The first deoxygenative coupling of amides by an unprecedented Sm/SmI{sub 2} system

Herein we report the novel finding that a samarium/samarium diiodide mixed reagent (Sm/SmI{sub 2}) successfully effects the deoxygenative coupling of amides, which provides a powerful tool for preparing vic-diaminoalkenes. However, a reaction system combining SmI{sub 2} with samarium metal accomplished deoxygenative coupling to provide vic-diaminoalkenes in excellent yields. As can be seen in the experiments varying the molar ratio of Sm/SmI{sub 2}, the yield of coupling product 2a was dependent on the amount of samarium metal (runs 1-3). More remarkable is the observation that magnesium metal (Mg{sup 2+}/Mg = -2.37 V), which has a reducing power similar to that of samarium metal (Sm{sup 3+}/Sm = -2.41 V), also effected the coupling of 1a in the presence of SmI{sub 2} (run 6). 17 refs., 2 tabs.