1,3-Diphenyl-2-propanone → 6,6-Dibenzylfulvene

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Reaction Steps

Into a 100 ml Kjeldahl flask purged thoroughly with nitrogen, equipped with a dropping funnel and a magnetic stirrer, were introduced cyclopentadiene 2.40 g (36.2 mmol) which had been subjected to cracking, and dehydrated tetrahydrofuran 50 ml. With cooling in an ice bath, 1.57 mol/L n-hexane solution of n-butyllithium, 24.3 ml (38.1 mmol), was dropwise added to the solution by means of the dropping funnel. The resulting slurry was stirred all night at room temperature. With the flask cooled in an ice bath, a solution of dibenzyl ketone 9.16 g (43.6 mmol) in 20 ml of dehydrated tetrahydrofuran, was dropwise added into the flask by means of the dropping funnel. The resulting slurry was stirred all night at room temperature. After addition of a saturated aqueous solution of ammonium chloride 50 ml and ether 50 ml, the organic phase was recovered with a separatory funnel. The water phase was extracted with ether 30 ml. The organic phase was washed twice with water 50 ml and once with a saturated salt solution 50 ml, and dried over magnesium sulfate. The solution was filtered to remove the magnesium sulfate, and the solvent of the filtrate was distilled away to obtain a solid. The residue was subjected to column chromatography to obtain an objective brown oil in 1.10 g (12%) yield. The 1H NMR spectrum and the FD-MS spectrum as measured with respect to the brown oil are given below:

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