A Concise Approach for the Synthesis of 6-Methoxy-2-Tetralone

The commercially available 6-methoxy-1-tetralone 1 was converted [15] into the olefin 2 in 94% yield by heating under reflux with 2,4-pentanediol and a catalytic amount of p-toluenesulphonic acid (p-TsOH) who’s spectroscopic properties perfectly agree with structure assigned. The olefin 2 was also previously synthesized by different routes [14,16] but the yield was not high compared with the present procedure. Epoxidation of the olefin 2 was performed with m-chloroperbenzoic acid (MCPBA) in dichloromethane and without purification the resulting epoxide was heated under reflux for 3 hours with ethanolic sulfuric acid (10%) to afford the tetralone 3 in 39% yield (overall yield 36%). The reaction was attempted several times using different reaction conditions which included change of temperature, time of heating, amount of sulfuric acid etc., (Table 1) however the yield could not be further improved. The spectroscopic data (NMR and MS) lent support to the assigned structure. An attempt was made to purify the epoxides by column chromatography but could not be isolated due to tendency of decomposition as exhibited in TLC. Table 1: Brief description of conditions for experiments of compound 3.