Catalyst-free hydroboration of CO2 with a nucleophilic diborane(4)

• Verfasst von: Frick, Markus [VerfasserIn]
• Verfasst von: Wadepohl, Hubert [VerfasserIn]
• Verfasst von: Kaifer, Elisabeth [VerfasserIn]
• Verfasst von: Himmel, Hans-Jörg [VerfasserIn]
• Titel: Catalyst-free hydroboration of CO2 with a nucleophilic diborane(4)
• Verf.angabe: Markus Frick, Julian Horn, Hubert Wadepohl, Elisabeth Kaifer, and Hans-Jörg Himmel
• E-Jahr: 2018
• Jahr: 11 September 2018
• Umfang: 4 S.
• Fussnoten: Im Titel ist „2“ tiefgestellt ; Gesehen am 24.07.2019
• Titel Quelle: Enthalten in: Chemistry - a European journal
• Ort Quelle: Weinheim : Wiley-VCH, 1995
• Jahr Quelle: 2018
• Band/Heft Quelle: 24(2018), 64, Seite 16983-16986
• ISSN Quelle: 1521-3765
• DOI: doi:10.1002/chem.201804612
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: B−B bond
• Sach-SW: carbon dioxide
• Sach-SW: diborane
• Sach-SW: hydroboration
• Sach-SW: nucleophilic boron
• K10plus-PPN: 166994171X

Abstract

Hydroboration generally requires the presence of a catalyst to lower the barrier for hydride transfer. This work reports on the first catalyst-free CO2 hydroboration with a neutral boron compound, the nucleophilic diborane [HB(hpp)]2, 1 (hpp=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate). Further hydroboration reactions to bis(boryl)acetals are possible. In acetonitrile, but not in dichloromethane solutions, hydroboration of a first CO2 is followed by hydroboration of a second CO2 molecule. Detailed kinetic measurements for both hydroboration steps were carried out and the influence of the solvent and the addition of a Lewis base on the rate constants analyzed. In contrast to catalyst-free hydroboration of CO2, hydroboration of the less electrophilic acetone requires the presence of an activating Lewis acid.