chloroformic acid ethyl ester; titanium tetrachloride; phosphorous acid trimethyl ester 1.) THF, -10 deg C, 5 min; 2.) THF, r.t., 15 h; 3.) CH2Cl2, reflux, 36 h; Yield given. Multistep reaction;

1.1: tetrahydrofuran / 0.08 h / -10 °C 1.2: tetrahydrofuran / 20 h / 20 °C 2.1: TiCl4 / CH2Cl2 / 41 h / Heating 3.1: 67 percent / H2O2; H2O; CH3COOH / 12 h / 80 °C 4.1: 5 h / Heating 5.1: NaOH; H2O / 12.67 h View Scheme

Multistep reaction;