[Cl:1][C:2]1[CH:3]=[C:4]2[C:12](=[CH:13][CH:14]=1)[O:11][C:7]1([CH2:10][CH2:9][CH2:8]1)[CH2:6]/[C:5]/2=[CH:15]\[C:16]([OH:18])=[O:17].[H][H]>C(OCC)(=O)C.[Pd]>[Cl:1][C:2]1[CH:3]=[C:4]2[C:12](=[CH:13][CH:14]=1)[O:11][C:7]1([CH2:8][CH2:9][CH2:10]1)[CH2:6][CH:5]2[CH2:15][C:16]([OH:18])=[O:17]To a stirred solution of (2E)-(6-chlorospiro[chromene-2,1′-cyclobutan]-4(3H)-ylidene)acetic acid (2.5 g, 9.444 mmol) in ethyl acetate (25 ml) was added 10% Pd/C (50 mg) at room temperature. The reaction mixture was stirred for 12 h at 40 psi hydrogen pressure in Paar hydrogenation apparatus. The reaction mixture was filtered through a celite bed, the filtrate was dried (Na2SO4) and concentrated to give 2.45 g of the product as a white solid; 1H NMR (300 MHz, CDCl3) δ 1.68-1.78 (m, 5H), 1.86-1.96 (m, 1H), 2.09-2.21 (m, 2H), 2.29-2.38 (m, 1H), 2.99 (d, J=13.2 Hz, 1H), 3.44 (br s, 1H), 6.73 (d, J=8.1 Hz, 1H), 7.04 (d, J=9.3 Hz, 1H).
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