triethylamine in benzene T=25°C; 1 h;

1: Bis(2,2,2-trifluoroethyl) phosphonate With N,N,N',N',N'',N''-hexamethylphosphoric triamide; sodium hydride in tetrahydrofuran T=20°C; Metallation; 2: ethyl α-bromobutyrate in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide T=20°C; Michaelis-Becker reaction; 9 h;

1: PCl5 / 0 - 75 °C 2: 1.43 g / triethylamine / benzene / 1 h / 25 °C View Scheme

18-crown-6 ether; sodium hexamethyldisilazane in tetrahydrofuran T=-78°C; 1.5 h; Title compound not separated from byproducts.;