1: trimethylsilyl 3,3-dimethylbutanoate With n-butyllithium; 1,1,1,3,3,3-hexamethyl-disilazane in tetrahydrofuran; hexane T=-78°C; 0.25 h; 2: chloro-trimethyl-silane in tetrahydrofuran; hexane T=-78 - 20°C; 12 h;

(i) LDA, THF, (ii) /BRN= 1209232/; Multistep reaction;

1.1: pyridine / tetrahydrofuran / 0.5 h / 0 °C 1.2: 61 percent / 1,1,1,3,3,3-hexamethyldisilazane / tetrahydrofuran / 12 h / 0 - 20 °C 2.1: 1,1,1,3,3,3-hexamethyldisilazane; n-BuLi / tetrahydrofuran; hexane / 0.25 h / -78 °C 2.2: 92 percent / tetrahydrofuran; hexane / 12 h / -78 - 20 °C View Scheme

3-chloro-benzenecarboperoxoic acid in hexane