Zusammenfassung

Chromium complexes have found very little applications as hydrogenation catalysts. Here, we report a Cr-catalyzed semi-hydrogenation of internal alkynes to the correspondingZ-alkenes with good stereocontrol (up to 99/1 for dialkyl alkynes). The catalyst comprises the commercial reagents chromium(III) acetylacetonate, Cr(acac)(3), and diisobutylaluminium hydride, DIBAL-H, in THF. The semi-hydrogenation operates at mild conditions (1-5 bar H-2, 30 degrees C).