Methyl p-toluenesulfonate → N-ethyl-2,3-diaza-spiro[4.4]non-3-ene-2-carboximidothioic acid methyl ester

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Reaction Steps

To a solution of 1.0 g (4.7 mmol) 2,3-diazaspiro[4.4]non-3-ene-2-carbothioic acid ethylamide in 10 mL methanol was added 1.1 g (5.7 mmol) methyl p-toluenesulfonate. The mixture was refluxed for 48 hrs and concentrated under reduced pressure. The residue was triturated with 30 mL diethyl ether and all volatiles were removed from the isolated oily product under reduced pressure. The residual oil was taken up in 40 mL dichloromethane and extracted 3 times with a saturated aqueous NaHCO3 solution. The organic layer was dried over MgSO4, filtered and evaporated to dryness under reduced pressure to afford 0.33 g (1.5 mmol, 31%) of N-ethyl-2,3-diaza-spiro[4.4]non-3-ene-2-carboximidothioic acid methyl ester as a light-brown oil. 1H NMR identical to spectrum obtained from material prepared by using iodomethane as methylating agent (vide supra).

Provenance & Evidence