Hydroboration of Terminal Alkenes and trans‐1, 2‐Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex. Issue 46 (13th October 2021)

• Record Type: Journal Article
• Authors: Weber, Stefan; Zobernig, Daniel; Stöger, Berthold; Veiros, Luis F.; Kirchner, Karl
• Is Part Of: Angewandte Chemie international edition. Volume 60:Issue 46(2021)
• Page Start: 24488
• Page End: 24492
• Publication Date: 2021-10-13
• Subjects: 1, 2-diboration -- alkenes -- alkynes -- hydroboration -- manganese alkyl complex; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202110736
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: A Mn I ‐catalyzed hydroboration of terminal alkenes and a 1, 2‐diboration of terminal alkynes with pinacolborane (HBPin) is described. For alkenes, anti‐Markovnikov hydroboration takes place; for alkynes the reaction proceeds with excellent trans‐1, 2‐selectivity. The most active pre‐catalyst is bench‐stable alkyl bisphosphine Mn I complex fac‐[Mn(dippe)(CO)3 (CH2 CH2 CH3 )]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn–alkyl bond to yield an acyl intermediate, which undergoes B−H bond cleavage of HBPin (for alkenes) and rapid C−H bond cleavage (for alkynes), forming the active Mn I boryl and acetylide catalysts [Mn(dippe)(CO)2 (BPin)] and [Mn(dippe)(CO)2 (C≡CR)], respectively. A broad variety of aromatic and aliphatic alkenes and alkynes was efficiently and selectively borylated. Mechanistic insights are provided based on experimental data and DFT calculations revealing that an acceptorless reaction is operating involving dihydrogen release. Abstract : A Mn I ‐catalyzed hydroboration of terminal alkenes and the 1, 2‐diboration of terminal alkynes with pinacolborane is described. In the case of alkenes anti ‐Markovnikov hydroboration takes place, while in the case of alkynes the reaction proceeds with trans ‐1, 2‐selectivity.