Triethylamine → 1,2a,4,5,6,6a,7,7a-Octahydrocyclobuta[a]inden-2-one

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Reaktionsschritte

A solution of 2-(2-allylcyclohexylidene)acetic acid (800 mg, 4.44 mmol) in dichloromethane (200 mL) was added Ghosez reagent (5.77 mmol, 0.795 mL) at room temperature. The solution was stirred for 45 min until the acid chloride was formed. Then N,N-dimethylaminopyridine (55 mg, 0.45 mmol) was added and the solution was heated to reflux. A solution of triethylamine (8.9 mmol, 1.25 mL) in dichloromethane (3.75 mL) was added dropwise over 30 min. The solution was refluxed for another 1 h and solvent was distilled off. Purification by flash chromatography (pentane/Et2O 95/5) gave 1,2a,4,5,6,6a,7,7a-octahydrocyclobuta[a]inden-2-one (600 mg, 83%) as a colourless liquid, with 20% of the tetrasubstituted regioisomere. 1H NMR (400 MHz, CDCl3) 5.59 (1H, brs), 3.92 (1H, brs), 3.21 (1H, dddd), 2.92 (1H, m), 2.73 (1H, m), 2.51 (1H, m), 2.04 (4H, m), 1.79 (1H, m), 1.48 (2H, m), 1.05 (1H, m).

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