First time asking a question but I've been trying to perform this reaction: 1,8 naphthalic anhydride reduction to diol

for quite a while now. Most of the times I've only gotten this far: to lactone

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).

from this paper: https://www-tandfonline-com.proxy.bc.edu/doi/full/10.1081/SCC-120038510?scroll=top&needAccess=true

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.

  • $\begingroup$ ZnCl2 is commercially available in ether soln under sureseal. Worth trying this rather than solid ZnCl2 $\endgroup$ – Waylander Mar 16 '18 at 18:21
  • $\begingroup$ The above option is a good one. Also, how are you drying your THF? Have you tried adding more equivalents of $\ce{LiAlH4}$? $\endgroup$ – ralk912 Mar 16 '18 at 18:50
  • $\begingroup$ My THF comes from an SPS. It takes me about 30 seconds to go from SPS to nitrogen-flushed two-neck with a dry needle. I'll certainly try both suggestions though. $\endgroup$ – Chemist581 Mar 19 '18 at 3:16

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