1: trimethylsilyl triflate / acetonitrile / 22 h / -40 - 20 °C 2: ammonia / methanol / 16 h / Ambient temperature View Scheme

1: trimethylsilyl triflate / acetonitrile / 24.5 h / -40 - 20 °C 2: ammonia / methanol / 16 h / Ambient temperature View Scheme

1: 1.) (NH4)2SO4, hexamethyldisilazane, 2.) trimethylsilyl triflate / 1.) reflux, overnight, 2.) MeCN, from -40 deg C to 0 deg C, 4 h 2: ammonia / methanol / 16 h / Ambient temperature View Scheme