Potassium Carbonate → 5-Hydroxy-2,2-dimethyl-8-oxo-10-propyl-2H,8H-pyrano[2,3-f]chromene-6-carbaldehyde

Participants

Reaction Conditions

Reaction Steps

To a solution of 6 (5.60 g, 22.5 mmol) in 2-butanone (125 mL) and dry DMF (10 mL) was added potassium carbonate (13.2 g, 95.5 mmol), tetrabutylammonium iodide (12.2 g, 33.0 mmol) and 3-chloro-3-methyl-1-butyne (11.2 g, 109 mmol). The reaction mixture was heated at 60° C. for 1 h, at which time anhydrous ZnCl2 (16 mL, 1 M solution in ether) was added. The reaction mixture was then heated at 60° C. for 12 h. Additional anhydrous ZnCl2 (8 mL, 1M solution in ether) was added, and the reaction mixture was kept at 60° C. for another 24 hr. The reaction mixture was cooled, quenched with saturated aqueous NH4Cl (150 mL), and extracted with EtOAc (3×100 mL). The combined organic layers were then washed with brine (1×50 mL), dried (MgSO4), concentrated and submitted to silica gel chromatography (solvent B) to obtain 7 (4.46 g, 63%) as a yellow solid: mp 116°-117° C.; 1H NMR (3:2 CDCl3 -CD3OD): δ 1.08 (t, J=7.3 Hz, 3H, --CH2CH3), 1.57 (s, 6H, --C(CH3)2), 1.68 (m, 2H, --CH2CH3), 2.90 (t, 2H, J=7.7 Hz, --CH2CH2CH3), 5.67 (d, 1H, J=10.0 Hz, H-3), 6.02 (s, 1H, H-9), 6.62 (d, 1H, J=10.0 Hz, H-4), 10.29 (s, 1H, --CHO); 13C NMR (3:2 CDCl3 -CD3OD): δ 12.79, 22.44, 27.15, 37.76, 79.87, 102.02, 103.08, 104.74, 110.18, 113.91, 126.31, 157.30, 157.54, 158.09, 158.91, 160.21, 192.12. Anal. Calcd for C18H18O5 : C, 68.78; H, 5.77. Found C, 68.77; H, 5.79.

Provenance & Evidence