Guanidine Hydrochloride → 5,6-dihydrobenzo[h]quinazolin-2-amine

Participants

Reaction Steps

α-Tetralone (5.00 g, 34.2 mmol) was heated with t-butoxy bis(dimethylamino)methane (5.96 g, 34.2 mMol) at 90° C. overnight. The solvent was removed under vacuum to give a brown oil. The oil was dissolved in anhydrous ethanol (80 mL) and treated with guanidine hydrochloride (6.53 g, 68.4 mmol) and sodium metal (1.64 g, 71.3 mmol). After the sodium dissolved, the mixture was heated under reflux for 46 h. The mixture was cooled to ambient temperature and guanidine hydrochloride (1.00 g) and sodium metal (0.4 g) were added. Heating was then continued for 24 h. The solvent was removed under vacuum. The residue was partitioned between chloroform and water. The organic layer was dried over anhydrous sodium sulfate and concentrated under vacuum. The residue was crystallized from ethanol to give 5,6-dihydrobenzo[h]quinazolin-2-amine as brown needles, 3.07 g; 1H NMR (DMSO-d6, 300 MHz) 8.08 (m, 2H), 7.24-7.40 (m, 3H), 6.40 (s, 1H), 2.81 (m, 2H), 2.68 (m, 2H) ppm; 13C-NMR (DMSO-d6, 75 MHz) 163.60, 159.09, 157.54, 140.14, 133.22, 131.02, 128.80, 127.37, 125.16, 117.15, 28.46, 23.80; MS (ES) 198 (M+H).

Provenance & Evidence