formic acid; ozone; zinc 1) CH2Cl2, -78 degC, 15 min; Yield given. Multistep reaction;

<b>Multi-step reaction with 2 steps<br /> </b>2: 1) N,N-carbonyldiimidazole / 1) THF, 25 degC, 5 h; 2) THF, irradiation<br /> <br /> &nbsp;

<b>Multi-step reaction with 2 steps<br /> </b>1: tetrahydrofuran / 16 h / Ambient temperature<br />2: tetrahydrofuran / 7 h / Irradiation<br /> <br /> &nbsp;