1: With diphenyl-phosphinic acid; triethylamine; tert-butyl alcohol 18 h; Heating; 2: With trifluoroacetic acid in dichloromethane T=0°C; 1 h;

1.1: NaH / dimethylformamide / 0.5 h / 20 °C 1.2: 80 percent / dimethylformamide / 48 h / 20 °C 2.1: H2SO4; NaNO2 / H2O / 0.33 h / 0 °C 2.2: 77 percent / H2O / 1 h / 120 °C 3.1: 88 percent / 1,5,7-triazabicyclo[4.4.0]dec-5-ene / acetonitrile / 20 h / 20 °C 4.1: 71 percent / 1 h / 230 °C 5.1: O3 / methanol / 0.5 h / -78 °C 5.2: dimethyl sulfide / methanol / -78 - 20 °C 6.1: 5.9 g / H3PO4 / H2O / 0.33 h / 100 °C 7.1: 90 percent / KOH / methanol; H2O / 1 h / Heating 8.1: DPPA; Et3N; t-BuOH / 18 h / Heating 8.2: TFA / CH2Cl2 / 1 h / 0 °C View Scheme

1.1: 88 percent / 1,5,7-triazabicyclo[4.4.0]dec-5-ene / acetonitrile / 20 h / 20 °C 2.1: 71 percent / 1 h / 230 °C 3.1: O3 / methanol / 0.5 h / -78 °C 3.2: dimethyl sulfide / methanol / -78 - 20 °C 4.1: 5.9 g / H3PO4 / H2O / 0.33 h / 100 °C 5.1: 90 percent / KOH / methanol; H2O / 1 h / Heating 6.1: DPPA; Et3N; t-BuOH / 18 h / Heating 6.2: TFA / CH2Cl2 / 1 h / 0 °C View Scheme

1.1: H2SO4; NaNO2 / H2O / 0.33 h / 0 °C 1.2: 77 percent / H2O / 1 h / 120 °C 2.1: 88 percent / 1,5,7-triazabicyclo[4.4.0]dec-5-ene / acetonitrile / 20 h / 20 °C 3.1: 71 percent / 1 h / 230 °C 4.1: O3 / methanol / 0.5 h / -78 °C 4.2: dimethyl sulfide / methanol / -78 - 20 °C 5.1: 5.9 g / H3PO4 / H2O / 0.33 h / 100 °C 6.1: 90 percent / KOH / methanol; H2O / 1 h / Heating 7.1: DPPA; Et3N; t-BuOH / 18 h / Heating 7.2: TFA / CH2Cl2 / 1 h / 0 °C View Scheme

1.1: 90 percent / KOH / methanol; H2O / 1 h / Heating 2.1: DPPA; Et3N; t-BuOH / 18 h / Heating 2.2: TFA / CH2Cl2 / 1 h / 0 °C View Scheme

1.1: 71 percent / 1 h / 230 °C 2.1: O3 / methanol / 0.5 h / -78 °C 2.2: dimethyl sulfide / methanol / -78 - 20 °C 3.1: 5.9 g / H3PO4 / H2O / 0.33 h / 100 °C 4.1: 90 percent / KOH / methanol; H2O / 1 h / Heating 5.1: DPPA; Et3N; t-BuOH / 18 h / Heating 5.2: TFA / CH2Cl2 / 1 h / 0 °C View Scheme

1.1: 5.9 g / H3PO4 / H2O / 0.33 h / 100 °C 2.1: 90 percent / KOH / methanol; H2O / 1 h / Heating 3.1: DPPA; Et3N; t-BuOH / 18 h / Heating 3.2: TFA / CH2Cl2 / 1 h / 0 °C View Scheme

1.1: O3 / methanol / 0.5 h / -78 °C 1.2: dimethyl sulfide / methanol / -78 - 20 °C 2.1: 5.9 g / H3PO4 / H2O / 0.33 h / 100 °C 3.1: 90 percent / KOH / methanol; H2O / 1 h / Heating 4.1: DPPA; Et3N; t-BuOH / 18 h / Heating 4.2: TFA / CH2Cl2 / 1 h / 0 °C View Scheme