1: malonic acid ethyl ester monopotassium salt With triethylamine; magnesium chloride in acetonitrile T=10 - 20°C; 2.5 h; Inert atmosphere; 2: cyclobutanecarbonyl chloride in acetonitrile T=0 - 20°C; 19 h; 3: With hydrogenchloride in water; ethyl acetate pH=5;

[2,2']bipyridinyl; n-butyllithium in tetrahydrofuran; hexanes T=-55 - 20°C;

diethyl ether; ammonia