Reaktion #732150

Reaktionsgleichung

4-methyl-α-tetralone

NaBH4

→

1,2-dihydro-1-methylnaphthalene

Lösungsmittel

methanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstige1,2-Dihydro-1-methylnaphthalene ((±)-8) was prepared
2. 2
   Sonstigeafter complete consumption of the starting material (approx. 2 h)
3. 3
   Sonstigewas quenched with saturated NaHCO3
4. 4
   ExtraktionThe aqueous layer was extracted with diethyl ether
5. 5
   Trocknendried with magnesium sulfate (MgSO4)
6. 6
   Filtrationfiltered
7. 7
   Sonstigethe solvent was removed under reduced pressure
8. 8
   workup.DISSOLUTIONThe crude alcohol was dissolved in toluene (15 mL)
9. 9
   workup.ADDITIONa few crystals of p-TsOH were added
10. 10
    workup.ADDITIONneutralized by slow addition of saturated sodium bicarbonate (NaHCO3)
11. 11
    Extraktionextracted with diethyl ether
12. 12
    WaschenThe combined organic layers where washed with brine
13. 13
    Trocknendried with magnesium sulfate (MgSO4)
14. 14
    Filtrationfiltered
15. 15
    Sonstigethe solvent was removed under reduced pressure
16. 16
    SonstigeThe product was purified by flash chromatography (SiO2, hexanes)

Vorschrift

1,2-Dihydro-1-methylnaphthalene ((±)-8) was prepared using a similar procedure to that reported in Ferraz et al., Tetrahedron, 57:1709ff (2001) (“Ferraz”), which is hereby incorporated by reference). The scheme is set forth in FIG. 7C. To a stirred solution of commercially available 4-methyl-α-tetralone (0.50 g, 3.12 mmol) in methanol (50 mL) was added NaBH4 (0.35 g, 9.36 mmol) portionwise. The reaction mixture was followed by TLC and, after complete consumption of the starting material (approx. 2 h), was quenched with saturated NaHCO3. The aqueous layer was extracted with diethyl ether, dried with magnesium sulfate (MgSO4), filtered, and the solvent was removed under reduced pressure. The crude alcohol was dissolved in toluene (15 mL), and a few crystals of p-TsOH were added. The reaction mixture was stirred overnight, then neutralized by slow addition of saturated sodium bicarbonate (NaHCO3) and extracted with diethyl ether. The combined organic layers where washed with brine, dried with magnesium sulfate (MgSO4), filtered, and the solvent was removed under reduced pressure. The product was purified by flash chromatography (SiO2, hexanes) to give 1,2-dihydro-1-methylnaphthalene ((±)-8) as a clear oil (0.35 g, 78% yield). The compound is volatile and cannot be dried for long periods (>30 min) under high vacuum. The spectroscopic data are consistent with previously reported data (Ferraz, which is hereby incorporated by reference).

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