selenium(IV) oxide in 1,4-dioxane; water T=90°C; 2.5 h;

1: vinyl-magnesium bromide With N,N'-dimethyl-N,N'-propyleneurea; copper(I) bromide dimethylsulfide complex in tetrahydrofuran T=-40°C; 0.25 h; 2: chloro-trimethyl-silane; 2-ethyl-cyclopent-2-enone in tetrahydrofuran T=-40 - -20°C; 1 h; 3: With triethylamine in tetrahydrofuran T=-20 - 20°C;