1: SOCl2, DMF / 3 h 2: 0.5 h 3: 1.) O3, 2.) (CH3)2S / 1.) MeOH, -70 deg C, 15 min, 2.) MeOH, RT, overnight 4: 85percent H3PO4 / 100 °C 5: 87 percent / 35percent aq. KOH / methanol / 100 °C View Scheme

1: SOCl2, DMF / 3 h 2: 0.5 h 3: 1.) O3, 2.) (CH3)2S / 1.) MeOH, -70 deg C, 15 min, 2.) MeOH, RT, overnight 4: 85percent H3PO4 / 100 °C View Scheme

T=220 - 230&deg;C;&nbsp;&nbsp;anschliessendes Behandeln mit wss. NaOH;&nbsp;<br /> &nbsp;