Celite; pyridinium chlorochromate in dichloromethane 30 h; Heatinghighly selective oxidative cleavage;

1: With Schwartz's reagent in tetrahydrofuran T=20°C; 1 h; 2: With tetrabutylammonium hexanitratocerate(IV) in tetrahydrofuran; N,N-dimethyl-formamide T=20°C; 12 h; Further stages.;