2,2-dimethyl-5-acetyl- 1,3-dioxane-4,6-dione/Acetyl-Meldrum’s acid

 The product has an R_f of 0.22 in 5% methanol/methylene chloride (silica gel) and displays the following spectral data: ¹H NMR (300 MHz, CDCl₃) δ: 1.71 (s, 6 H), 2.64 (s, 3 H) ; ¹³C (75 MHz, CDCl₃) δ: 37.5, 42.4, 45.1, 106.2, 118.6, 174.8, 184.2, 207.5 .  The acidic proton was not observed in the ¹H NMR spectrum.

lightyellow plate, mp 87.6-88.0°C

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Endo-tricyclo[6.2.1.02,7]undeca-4,9-diene-3,6-dione

Synthesis of endo-tricyclo[6.2.1.0^2,7]undeca-4,9-diene-3,6-dione (3)

To a solution containing 541 mg (5.0 mmol) in 18 mL of dry methanol at -78º C under nitrogen atmosphere, was added cyclopentadiene freshly distilled (344 mg, 5.2 mmol, in 4 mL of dry methanol) also cooled to -78ÚC. Then, the reaction mixture was allowed to reach 0 ÚC (approx. 1h). After that, the solvent was removed under reduced pressure and the product was crystallized by using hexane, yielding the yellow crystals (854 mg, 4.9 mmol, 98%). 

mp. 63-65º C. 

¹H NMR (CDCl₃, 400 MHz), δ (ppm) 1.44 (dt, 1H, J 8.4 Hz and J 1.7 Hz; 1.55 (dt, 1H, J 8.4 Hz, J 1.7 Hz), 3.20-3.26 (m, 2H), 3.53 - 3.58 (m, 2H), 6.07 (t, 2H, J 1.7 Hz), 6.58 (sl, 2H). 

¹³C NMR (100 MHz, CDCl₃), δ (ppm) 48.3, 48.7 (2 x CH and 1 x CH₂), 135.3, 142.0, 199.4.