Aluminium as an electron pool for organic synthesis - Multi-metal redox promoted reactions

Aluminum (A1) is an ideal reducing agent (electron pool) since it is cheap, easy to handle, able to release enough electron (3 e^-/atom), and environment friendly. However, the use of A1 in organic synthesis is rather limited owing to lack of efficient electron transfer process between A1 and organic substances. In last decay, we and some other groups developed multi-redox promoted reactions using A1 as a terminal reductant in which A1 act as an electron pool and a catalytic amount of metal salt(s) works as a mediator for electron transfer from A1 to substrates. Indeed, various combinations of A1 and metal salt(s), e.g., A1/PbBr₂, A1/PbBr₂/A1Br₃, A1/NiCl₂/CrCl₂, A1/PbBr₂/TFA, A1/PbBr₂/NiCl₂(bpy), etc., have been developed to promote carbon-carbon bond formation as well as highly selective functionalization. Further more, these multi-redox promoted reactions have been successfully utilized for the synthesis of useful compounds, such as β-lactam antibiotics and β-lactamase inhibitors. This review article will summarize the recent progress in the multi-metal redox promoted reactions using A1 as an electron pool and their applications to organic synthesis.