1: Bu2(Me)PO3 With n-butyllithium in tetrahydrofuran T=-78°C; 0.5 h; 2: With copper(l) chloride in tetrahydrofuran T=-78 - -30°C; 1 h; 3: chloroacetyl chloride in tetrahydrofuran; diethyl ether T=-30 - 20°C;