(i) KOtBu, tBuOH, (ii) aq. HBF4, MeCN, (iii) LiOH, trialkyl-methyl-ammonium chloride, benzene; Multistep reaction;

1: MeCS2Me With methyllithium in tetrahydrofuran; diethyl ether T=-78°C; 0.25 h; 2: With rac N-phenylsulfonyl tert-butyl methyl oxaziridine in tetrahydrofuran; diethyl ether T=-78°C; 0.333333 h; 3: methyl iodide in tetrahydrofuran; diethyl ether T=-78 - 20°C;

3-chloro-benzenecarboperoxoic acid in dichloromethane

potassium hydroxide in benzene