dimethylsulfide borane complex in tetrahydrofuran T=40°C; 4 h;

1: 66 percent / 2.) H2SO4 / 1.) THF, 40 deg C, 12 h; 2.) THF/H2O 2: 70 percent / (i-Pr)2EtN / CH2Cl2 / -50 up to 23 deg C witthin 4 h 3: catecholborane, chiral oxazaborolidine / CH2Cl2 / 1.) -78 up to -40 deg C; 2.) -40 deg C, 36 h 4: n-butyl ammonium formate, Pd(Ph3P)4 / CH2Cl2; methanol / 3 h / 23 °C 5: 87 percent / KN(SiMe3)2 / tetrahydrofuran / 8 h / -78 °C 6: 77 percent / BH3*Me2S / tetrahydrofuran / 4 h / 40 °C View Scheme

1: 70 percent / (i-Pr)2EtN / CH2Cl2 / -50 up to 23 deg C witthin 4 h 2: catecholborane, chiral oxazaborolidine / CH2Cl2 / 1.) -78 up to -40 deg C; 2.) -40 deg C, 36 h 3: n-butyl ammonium formate, Pd(Ph3P)4 / CH2Cl2; methanol / 3 h / 23 °C 4: 87 percent / KN(SiMe3)2 / tetrahydrofuran / 8 h / -78 °C 5: 77 percent / BH3*Me2S / tetrahydrofuran / 4 h / 40 °C View Scheme

1: 66 percent / 2.) H2SO4 / 1.) THF, 40 deg C, 12 h; 2.) THF/H2O 2: 70 percent / (i-Pr)2EtN / CH2Cl2 / -50 up to 23 deg C witthin 4 h 3: catecholborane, chiral oxazaborolidine / CH2Cl2 / 1.) -78 up to -40 deg C; 2.) -40 deg C, 36 h 4: n-butyl ammonium formate, Pd(Ph3P)4 / CH2Cl2; methanol / 3 h / 23 °C 5: 87 percent / KN(SiMe3)2 / tetrahydrofuran / 8 h / -78 °C 6: 77 percent / BH3*Me2S / tetrahydrofuran / 4 h / 40 °C View Scheme

1: 87 percent / KN(SiMe3)2 / tetrahydrofuran / 8 h / -78 °C 2: 77 percent / BH3*Me2S / tetrahydrofuran / 4 h / 40 °C View Scheme