An Alkene‐Promoted Borane‐Catalyzed Highly Stereoselective Hydrogenation of Alkynes to Give Z‐ and E‐Alkenes. Issue 8 (14th January 2015)

• Record Type: Journal Article
• Authors: Liu, Yongbing; Hu, Lianrui; Chen, Hui; Du, Haifeng
• Is Part Of: Chemistry. Volume 21:Issue 8(2015)
• Page Start: 3495
• Page End: 3501
• Publication Date: 2015-01-14
• Subjects: alkene -- alkyne -- hydrogenation -- metal‐free catalysis -- stereoselectivity; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201405388
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The stereoselective hydrogenation of alkynes to alkenes is an extremely useful transformation in synthetic chemistry. Despite numerous reports for the synthesis of Z ‐alkenes, the hydrogenation of alkynes to give E ‐alkenes is still not well resolved. In particular, selective preparation of both Z ‐ and E ‐alkenes by the same catalytic hydrogenation system using molecular H2 has rarely been reported. In this paper, a novel strategy of using simple alkenes as promoters for the HB(C6 F5 )2 ‐catalyzed metal‐free hydrogenation of alkynes was adopted. Significantly, both Z ‐ and E ‐alkenes can be furnished by hydrogenation with molecular H2 in high yields with excellent stereoselectivities. Further experimental and theoretical mechanistic studies suggest that interactions between H and F atoms of the alkene promoter, borane intermediate, and H2 play an essential role in promoting the hydrogenolysis reaction. Abstract : With a little help from an alkene! A HB(C6 F5 )2 ‐catalyzed metal‐free hydrogenation of alkynes, promoted by an alkene through HF interactions, was successfully achieved. Z ‐ and E ‐alkenes can be accessed respectively in high yields with excellent stereoselectivities (see scheme; TS=transition state).