Phenyl Isothiocyanate → tert-butyl 5,5-dimethyl-2-(3-phenylthioureido)-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylate

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Reaction Steps

To a solution of tert-butyl 2-amino-5,5-dimethyl-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylate (0.100 g, 0.353 mmol, 1 eq) in dry tetrahyrofuran (5 mL) under argon was added phenyl isothiocyanate (0.05 mL, 0.388 mmol, 1.1 eq). The mixture was heated at reflux for 16 hours. The solvent was evaporated in vacuo. Purification by reverse-phase chromatography (0-100% CH3CN: Water ramp over 20 min) afforded the desired product tert-butyl 5,5-dimethyl-2-(3-phenylthioureido)-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylate as a yellow solid (0.045 g, 0.108 mmol, 30% yield). 1H NMR (400 MHz, DMSO) δ 11.92 (s, 1H), 11.05 (s, 1H), 7.50 (d, J=7.6, 2H), 7.42 (t, J=7.9, 2H), 7.26 (t, J=7.3, 1H), 4.61 (s, 2H), 2.65 (s, 2H), 1.53 (s, 9H), 1.23 (s, 6H).

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