dipyridinium dichromate; 4 A molecular sieve in N,N-dimethyl-formamide T=20°C; 48 h;

1.1: 90 percent / pyridinium dichromate; 4 Angstroem molecular sieves / dimethylformamide / 48 h / 20 °C 2.1: 99 percent / sodium borohydride; cerium(III) chloride heptahydrate / methanol / 0.5 h / 0 - 5 °C 3.1: triphenylphosphine; DIAD / tetrahydrofuran / 0.67 h / 0 - 20 °C 3.2: 74 percent / tetrahydrofuran / 20 °C 4.1: 99 percent / TFA; MeOH / 1,2-dichloro-ethane / 20 °C View Scheme