1: 4-methyl-benzaldehyde; toluene-4-sulfonamide With N-chloro-succinimide; tin(ll) chloride in dichloromethane T=0°C; 2: α,α-diisopropylhomoallylic alcohol With N-chloro-succinimide; tin(ll) chloride in dichloromethane T=-40°C; 3: in dichloromethane 21 h;