Ammonium Chloride → 1-(8-Benzyl-1,4-dioxaspiro[4.5]dec-8-yl)pyrrolidine

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Reaction Steps

A solution of 40.0 g 8-pyrrolidin-1-yl-1,4-dioxaspiro[4.5]decane-8-carbonitrile in 150 ml analytical grade tetrahydrofuran was added dropwise to 127 ml 2.0 molar benzylmagnesium chloride solution in THF under a nitrogen atmosphere and the mixture was stirred overnight at room temperature. For working up, 50 ml saturated ammonium chloride solution were added, while cooling with ice, the phases were separated, the aqueous phase was extracted three times with 50 ml diethyl ether each time, the combined organic phases were dried over sodium sulfate, filtered and concentrated and the residue was largely freed from solvent residues in vacuo. The crude 1-(8-benzyl-1,4-dioxaspiro[4.5]dec-8-yl)pyrrolidine obtained (54.0 g of yellow solid) was stirred, without further purification, with a mixture of 128 ml conc. hydrochloric acid (32 per cent by weight) and 74 ml water for 24 hours at room temperature. The reaction mixture was then first washed twice with 50 ml diethyl ether each time and then rendered alkaline by addition of sodium hydroxide solution (32 per cent by weight), while cooling with ice, and extracted three times with 100 ml methylene chloride each time, the combined methylene chloride extracts were dried over sodium sulfate, filtered and concentrated and the residue was largely freed from solvent residues in vacuo. 40.3 g 4-benzyl-4-pyrrolidin-1-yl-cyclohexanone were obtained.

Provenance & Evidence