1: cyclopentanone With chloro-trimethyl-silane; lithium diisopropyl amide in tetrahydrofuran T=0°C; Michael addition; 2 h; 2: 4-methyl-pent-3-en-2-one With titanium tetrachloride in dichloromethane T=-78°C; Michael addition; 1 h;

titanium tetrachloride in dichloromethane T=-78°C;