Synthesis
General procedure for the synthesis of 2-butoxynaphthalene from bromobutane and 2-naphthol: 0.14 g (1.0 mmol) of a mixture of 1-naphthol and 2-naphthol was mixed with 1.0 mmol of an alkali metal carbonate (0.14 g of K2CO3 or 0.33 g of Cs2CO3), to which was added in specific cases 11.4 mg (0.05 mmol) of TEBAC and 1.2 mmol of alkyl halide (e.g., 0.14 ml of benzyl bromide, 0.10 ml of ethyl iodide, 0.12 mol of butyl bromide, or 0.11 ml of isopropyl bromide) in a closed vial. The reaction was carried out in a CEM microwave reactor at 20-30 W [or 300 W] for an appropriate time at 125°C. After completion of the reaction, the mixture was dissolved in 25 ml of ethyl acetate and the suspension was filtered. The volatile components were removed by evaporation to give a crude product. The crude product is initially purified by passing through a silica gel layer about 2-3 cm thick, using ethyl acetate as eluent, and analyzed by GC-MS or GC. Similar reactions can be carried out with 3 ml of MeCN as solvent and the post-treatment steps are similar to the solvent-free alkylation described above, but without the addition of ethyl acetoacetate. The major products such as compounds 2, 7, 8, 10a-c and 13a,b were obtained in pure form by repeated chromatography. Control experiments were carried out in a similar manner using benzyl bromide under conventional heating conditions.
References
[1] Chemical Communications, 1998, # 20, p. 2245 - 2246
[2] Letters in Organic Chemistry, 2013, vol. 10, # 5, p. 330 - 336
