1: 2-(trimethylsilyl)-1,3-dithiane With cyclohexane; sec.-butyllithium in tetrahydrofuran; hexane T=-70 - 0°C; Inert atmosphere; 2: 4-ketocyclohexanecarboxylic acid ethyl ester in tetrahydrofuran; hexane T=-70 - 20°C; 6 h; Inert atmosphere;