Alkali metals in silica gel (M-SG) have been developed at Michigan State University as dry, free flowing powders which can replace dissolving metal conditions, typically requiring liquid ammonia, for carrying out reductions and other transformations.

The first paper¹ describes the Birch reduction of a number of polycyclic aromatic compounds in good to excellent yield (74-100%).  There are 11 examples but most of these concern molecules with limited functionality (acridine, phenazene and quinoline for example).  Olefinic and acetylenic bonds are reduced in preference to aromatic rings (stilbene and diphenylacetylene are both reduced to 1,2-diphenylethane and indene is reduced to indane).  The only halogenated substrate, 9-chloromethylanthracene, undergoes dechlorination and Birch reduction producing 9-methyl-9,10-dihydroanthracene.

M-SG reagents are commercially available from SiGNa Chemistry Inc who have also published their results on similar Birch reductions but also include some examples with methoxy substituents2.

1. P. Nandi, J.L. Dye, and J.E. Jackson, J. Org. Chem., 2009, 74, 5790-5792.
2. M.J. Costanzo, M.N. Patel, K.A. Petersen, and P.F. Vogt, Tet. Letts., 2009, 50, 5463-5466.