GENERAL PROCEDURE: A representative procedure for the synthesis of 3,3-dimethyl-3,4-dihydroquinoxalin-2(1H)-ones from o-phenylenediamine and trichloro-tert-butanol is as follows: under nitrogen protection, 50% aqueous sodium hydroxide (0.42 mL, 5 equiv.) was added slowly and dropwise to cooled-to-0 °C o-phenylenediamine 1a (200 mg, 1 equiv.), 4-(trichloromethyl)tetrahydro-2H-pyran -4-ol (812 mg, 2 eq.) and N-benzyl-N,N-diethylethanaminium chloride (42 mg, 0.1 eq.) in dichloromethane (0.1 M) in a stirred mixture with a controlled dropwise addition time of 10-20 seconds. The reaction mixture was stirred at 0 °C and then gradually warmed to room temperature and continued stirring for 18 hours. The reaction process was monitored by analytical HPLC-MS. Upon completion of the reaction, the mixture was diluted with water (10 mL) until all solids were dissolved and the layers were subsequently separated. The aqueous layer was extracted with dichloromethane (3 x 20 mL). The organic layers were combined, dried with magnesium sulfate, filtered and the solvent evaporated to give the crude product. The crude product was purified by silica gel column chromatography with an elution gradient of 0-50% ethyl acetate/heptane. The purified solid was filtered through a Brinell funnel and washed with methyl tert-butyl ether (2×10 mL) to give the final 10,2,3,40,5,6-hexahydro-30H-spiro[pyran-4,20-quinoxalin]-30-one (310 mg, 77%) as a pale yellow powder.
