Here is the procedure I've been following: Dry THF (20 mL), LiAlH4 (6 mmol) and anhydrous ZnCl2 (3 mmol) were added in a 100 mL round‐bottom flask fitted with a CaCl2 guard tube and mounted over a magnetic stirrer. 1,8‐Naphthalic anhydride (0.99 g, 5 mmol) was added into the flask slowly at room temperature. After 6 hr, the excess LiAlH4 was destroyed by addition of 5 mL water, and the mixture was adjusted with 1 N HCl to weak acidity. The resultant two‐phase solution was extracted with ethyl acetate (3 × 15 mL), washed with brine and then dried over anhydrous MgSO4. After the solvent was evaporated, the crude product was recrystallized with benzene and methanol (1/1) to give white crystals 0.790 g (84.1% yield). M.p.: 161–163°C (lit.2c Boekelheide, B. and Vick, G. K. 1956. A synthesis of pleiadiene and acepleiadylene. J. Am. Chem. Soc., 78: 653 [Google Scholar] 157–158°C); ESI‐MS (m/z): 171 (M + H − H2O)+, 189 (M)+; IR (cm−1): 3345, 3241, 1601, 1510,1425, 1366, 1320, 1058, 1035, 1013, 998, 826, 774.724; 1H NMR (600 MHz, CD3COCD3), δ4.54 (s, 2H), 5.27 (s, 4H), 7.44 (t, 2H, J = 7.5 Hz), 7.64 (d, 2H, J = 7.2 Hz), 7.87 (d, 2H, J = 7.8 Hz).
I've tried using ZnCl2, but it's hygroscopic so picks up water in the atmosphere and destroys my LAH (this is my hypothesis). I also tried refluxing for 8 hours and again only got the second product before my THF evaporated. Do you guys have any suggestions? Thanks in advance.