Mechanistic and Synthetic Studies of Biaryl Birch Reductions

The Birch reduction of biaryls generally converts one of the two arenes into a cyclohexa-1,4-diene. Biaryls are more reactive than monocyclic arenes under the Birch conditions. Unlike the reduction of monocyclic arenes, biaryl reduction proceeds through two consecutive electron transfer steps before the protonation of the dianion intermedi-ate. The biaryl reductions and subsequent alkylations in one pot rapidly increase the molecular complexity and thus have been used in the syn-thesis of natural products and drug-like molecules.1 Introduction2 The Physical Organic Chemistry of the Birch Reduction of Biaryls3 Biaryls as the Mediators of Electron Transfer4 Methods for the Dissolving-Metal Reduction of Biaryls5 Intercepting the Biaryl Reduction Intermediates with Electro-philes6 Synthetic Applications of the Dissolving-Metal-Mediated Reduc-tions of Biaryls7 Outlook