Cerium(III) chloride → 3-Naphthalen-2-yl-cyclopent-2-enol

Reaction equation

[CH:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH:4]=[CH:3][C:2]=1[C:11]1[CH2:15][CH2:14][C:13](=[O:16])[CH:12]=1.[Cl-].[Cl-].[Cl-].[Ce+3].[BH4-].[Na+]>C(O)C>[CH:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH:4]=[CH:3][C:2]=1[C:11]1[CH2:15][CH2:14][CH:13]([OH:16])[CH:12]=1

Participants

Procedure

A solution of 3-(naphthalen-2-yl)cyclopent-2-enone (2.22 g, 10.7 mmol) in ethanol (250 mL) was treated with cerium trichloride (2.63 g, 10.7 mmol, 1 eq.) followed portion wise by sodium borohydride (0.48 g, 12.8 mmol, 1.2 eq.) at room temperature. The reaction mixture was stirred for 0.5 h, then quenched with saturated aqueous ammonium chloride (125 mL) and concentrated to remove ethanol. The concentrate was diluted with water (125 mL) and extracted with dichloromethane (3×125 mL). The combined organic extracts were dried over magnesium sulphate, filtered, and concentrated in vacuo to afford in a quantitative yield as a white solid which was not further purified. 1H NMR (400 MHz, CDCl3) δ ppm 1.89-1.97 (1H, m, CH), 2.48-2.57 (1H, m, CH), 2.75-2.83 (1H, m, CH), 3.00-3.09 (1H, m, CH), 3.27 (1H, q, J 1.3 Hz, CH), 5.04-5.09 (1H, m, OH), 6.36 (1H, q, J 1.9 Hz, CH), 7.39-7.50 (2H, m ArH), 7.70 (1H, dd, J 1.6, 8.5 Hz, ArH), 7.75-7.88 (3H, m, ArH), 7.99 (1H, s, ArH).