1: 1.) CuI, 2.) N,N'-(dimethylpropylene)urea, (EtO)3P / 1.) THF, -35 deg C, 15 min, 2.) THF, from -35 deg C to RT 2: Ti(Oi-Pr)4, i-PrMgCl / diethyl ether / a) -45 to -40 deg C, 1 h, b) from -40 deg C to RT, 90 min, c) RT, 2 h 3: FeCl3, pyridine / dimethylformamide / 0.5 h / Ambient temperature 4: NaOAc / methanol / 1 h / Ambient temperature View Scheme

tetrabutyl ammonium fluoride in tetrahydrofuran

1: 55 percent / tetrabutylammonium fluoride / tetrahydrofuran 2: 73 percent / tetrahydrofuran; diethyl ether / 1 h / -30 °C View Scheme