1174321-06-2

A3-5 (1.5 g, 6.5 mmol) was dissolved in dichloromethane (DCM, 20 mL) at 0 °C and trifluoroacetic acid (TFA, 2 mL) was added slowly and dropwise. The reaction mixture was stirred at room temperature for 4 hours. Upon completion of the reaction, the solvent was removed by concentration under reduced pressure to afford the product A3-6 (1 g, 88% yield). The structure of the product was confirmed by 1H NMR (400 MHz, MeOD): δ 9.30 (s, 1H), 8.98 (s, 1H), 6.92 (t, J = 14.4 Hz, 1H).

[1] Patent: WO2012/138734, 2012, A1. Location in patent: Page/Page column 65-66
[2] Patent: US2009/209755, 2009, A1. Location in patent: Page/Page column 54-55
[3] Patent: US2010/93999, 2010, A1. Location in patent: Page/Page column 49
[4] Patent: WO2011/9897, 2011, A1. Location in patent: Page/Page column 74; 76
[5] Patent: WO2011/9898, 2011, A1. Location in patent: Page/Page column 86; 87