The Metal-Ammonia Reduction of 1-Naphthoic Acid

The reduction of aromatic compounds with alkali metals in liquid anhydrous ammonia (Birch Reduction and its modifications) has developed as an effective method for the synthesis of 1,4-cyclohexadiene derivatives, and has been the subject of several reviews.^1,2 In many cases, particularly with polynuclear compounds,² the reaction is complicated by subsequent isomerizations, and/or the reduction of initial products which are often themselves subject to reduction under the reaction conditions. Recently, we have shown that inverse quenching techniques can provide a substantial improvement in this reduction reaction by minimizing the effect of excess metal during the quenching process.³ Application of these methods to 1-naphthoic acid 1 have not only provided an excellent synthesis of 1,4-dihydro-1-naphthoic acid, but we believe will furnish a much improved general technique f o r the reduction of polynuclear aromatic carboxylic acids.