vanadium pentoxide in methanol 0 deg C, then RT, 2 h;

<b>Multi-step reaction with 2 steps<br /> </b>1: O₂ / CDCl₃; various solvent(s) / 3 h / -78 &deg;C / Irradiation; TPP<br />2: CDCl₃ / 0 deg C, then 20 deg C, 30 min<br /> <br /> &nbsp;