## 3 Materials and Methods
### Chemical Syntheses  
#### 3.2.1 Preparation of 2-Amino-7-morpholinobenzo[_d_]thiazol-4-ol (**2**)  
A solution of 2-amino-4-methoxy-7-morpholinobenzodiaazole **1** (1.3 g, 5 mmol) in 48% HBr (8.9 M, 50 mL, 445 mmol, good quality: colorless to slightly yellowish) was stirred at 130 \({}^{\circ}\)C for 24 h. The resulting suspension was cooled to ambient temperature and left to stand overnight at 5 \({}^{\circ}\)C. The grey-brown solid was then collected by filtration and taken up into water (50-60 mL). Under efficient stirring, the mixture was titrated with 10 N aqueous sodium hydroxide until a precipitate started to form, followed by saturated aqueous sodium bicarbonate until the pH reached 8-9. The resulting suspension was diluted with water (50 mL), stirred for 10 min at ambient temperature and left to stand at 5 \({}^{\circ}\)C for one hour. The product was collected by filtration, washed with water and dried in an oven at 100 \({}^{\circ}\)C to afford the title compound (1.15 g, 85%) as a tan solid (TLC: ethyl acetate/MeOH/AcOH, 98/2/0.2, R\({}_{\mathrm{f}}\) 0.69; ethyl acetate/hexane/AcOH, 80/20/0.2, R\({}_{\mathrm{f}}\) 0.57), mp 267 \({}^{\circ}\)C (dec). The product was soluble in 0.5 N NaOH. \({}^{1}\)H-NMR (400 MHz, DMSO-\(d_{6}\)) & 2.90 (t, 4H, \(J\) = 4.5 Hz, CH\({}_{2}\)NCH\({}_{2}\)), 3.72 (t, 4H, \(J\) = 4.5 Hz, CH\({}_{2}\)OCH\({}_{2}\)), 6.55 (d, 1H, \(J\) = 8.4 Hz, H\({}^{6}\)), 6.61 (d, 1H, \(J\) = 8.4 Hz, H\({}^{5}\)), 7.23 (s\({}_{\mathrm{br}}\), 2H, NH\({}_{2}\)), 8.89 (s, 1H, OH). \({}^{13}\)C-NMR (100 MHz, DMSO-\(d_{6}\)) & 51.8 (CNC), 67.1 (COC), 111.3 (C\({}^{5}\)), 112.1 (C\({}^{6}\)), 126.2 (C\({}^{7a}\)), 138.8 (C\({}^{3a}\)), 142.3 (C\({}^{7}\)), 144.5 (C\({}^{4}\)), 165.1 (C\({}^{2}\)). Anal. calcd for C\({}_{11}\)H\({}_{13}\)N\({}_{3}\)O\({}_{2}\)S: C, 52.57; H, 5.21; N, 16.72; found: C, 52.55; H, 5.17; N, 16.74. HRMS \(m/z\): [M + H]\({}^{+}\) calcd: 252.0801; found: 252.0796. 3.2.2. Preparation of (_E_)-\(N^{\prime}\)-(4-Hydroxy-7-morpholinobenzo[_d_]thiazol-2-yl)-\(N\),\(N\)-dimethylformamidine (**3**)  
N,N-Dimethylformamide dimethyl acetal (160 \(\mu\)L, 1.2 mmol) was added to a solution of **2** (251 mg, 1 mmol) in anhydrous DMF (7 mL) and the mixture was stirred at 60 \({}^{\circ}\)C for 30 min (TLC: ethyl acetate/hexane/AcOH, 80/20/0.2, \(R_{\rm{fsm}}\) 0.56, \(R_{\rm{fp}}\) 0.25-0.39 extended spot). The reaction mixture was cooled to ambient temperature, poured into ice/half-saturated brine (50:50, 100 mL) and stirred for 10 min. Crystallization was induced by scratching with a glass rod and the mixture was left to stand at 5 \({}^{\circ}\)C overnight. The resulting precipitate was collected by filtration and dried at 100 \({}^{\circ}\)C to afford the title compound (280 mg, 91%) as off-white crystals, mp 244 \({}^{\circ}\)C (dec.). 1H-NMR (400 MHz, DMSO-\(d_{6}\)) 8 2.94 (t, 4H, \(J\) = 4.5 Hz, \(CH_{2}\)N\(CH_{2}\)), 3.02 (s, 3H, N-CH\({}_{3}\)), 3.16 (s, 3H, N-CH\({}_{3}\)), 3.73 (t, 4H, \(J\) = 4.5 Hz, \(CH_{2}\)OCH\({}_{2}\)), 6.56 (d, 1H, \(J\) = 8.4 Hz, \(H^{6}\)), 6.69 (d, 1H, \(J\) = 8.4 Hz, \(H^{5}\)), 8.38 (s, 1H, N-CH), 9.27 (s, 1H, OH). \({}^{13}\)C-NMR (100 MHz, DMSO-\(d_{6}\)) 8 35.1 (N-CH\({}_{3}\)), 40.8 (N-CH\({}_{3}\)), 51.8 (CNC), 67.1 (COC), 111.7 (\(C^{5}\)), 112.9 (\(C^{6}\)), 127.6 (\(C^{72}\)), 138.8 (C\({}^{33}\)), 141.8 (\(C^{7}\)), 146.0 (\(C^{4}\)), 158.1 (N-CH), 170.7 (\(C^{2}\)). Anal. calcd for C\({}_{14}\)H\({}_{18}\)N\({}_{4}\)O\({}_{2}\)S: C, 54.88; H, 5.92; N, 18.29; found: C, 54.86; H, 5.89; N, 18.31. HRMS \(m/z\): [M + H]\({}^{+}\) calcd: 307.1223; found: 307.1220. 2.3 Preparation of (_E_)-\(N^{\prime}\)-(4-Benzyloxy-7-morpholinobenzo[_d_]thiazol-2-yl)-\(N\),\(N\)-dimethylformamidine (**4**)  
Cs\({}_{2}\)CO\({}_{3}\) (489 mg, 1.5 mmol) was added, followed by benzyl bromide (155 \(\mu\)L, 1.3 mmol), under argon to a stirred solution of **3** (306 mg, 1 mmol) in anhydrous DMF (5 mL).