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syn-1,2-carboboration of alkynes with borenium cations.

Cade IA, Ingleson MJ - Chemistry (2014)

Bottom Line: All the prepared borenium cations are highly chlorophilic and exhibit significant interaction with AlCl4(-) resulting in an equilibrium concentration of Lewis acidic "AlCl3" species.In contrast, QOBPh(+) and QOBTh(+) systems effect the syn-1,2-carboboration of 3-hexyne.DFT calculations at the M06-2X/6-311G(d,p)/PCM(DCM) level confirm that the higher migratory aptitude of Ph versus Me leads to a lower barrier to 1,2-carboboration relative to 1,1-carboboration.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL (UK).

No MeSH data available.


Synthesis of QOBCl2 and QOBClR from QOSiMe3 and ahaloborane. R=Phenyl (QOBPhCl) and (5-hexyl)thienyl (QOBThCl).Single-crystal X-ray structures are shown for: QOBClPh andQOBCl2, thermal ellipsoids at the 50 % probability level.
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sch03: Synthesis of QOBCl2 and QOBClR from QOSiMe3 and ahaloborane. R=Phenyl (QOBPhCl) and (5-hexyl)thienyl (QOBThCl).Single-crystal X-ray structures are shown for: QOBClPh andQOBCl2, thermal ellipsoids at the 50 % probability level.

Mentions: The 4-coordinate quinolato-chloroborane precursors are afforded by mixing the chloroborane withQOSiMe3 (Scheme 3), followed bywashing with pentane to remove any unreacted BCl3/RBCl2 and/orQOSiMe3. The final step en route to borenium formation is abstraction of thechloride ligand with aluminium trichloride concomitantly forming the tetrachloroaluminate counterion(Scheme 4). In previous studies this anion has been shown tobe both stable and weakly coordinating towards highly electrophilic borenium centres unlike otherclassic weakly coordinating anions (WCA).13 However, afeature of the quinolato architecture is the presence, even when coordinated to boron, of a mildlyLewis basic site at oxygen that complicates the reactivity with AlCl3.


syn-1,2-carboboration of alkynes with borenium cations.

Cade IA, Ingleson MJ - Chemistry (2014)

Synthesis of QOBCl2 and QOBClR from QOSiMe3 and ahaloborane. R=Phenyl (QOBPhCl) and (5-hexyl)thienyl (QOBThCl).Single-crystal X-ray structures are shown for: QOBClPh andQOBCl2, thermal ellipsoids at the 50 % probability level.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4209141&req=5

sch03: Synthesis of QOBCl2 and QOBClR from QOSiMe3 and ahaloborane. R=Phenyl (QOBPhCl) and (5-hexyl)thienyl (QOBThCl).Single-crystal X-ray structures are shown for: QOBClPh andQOBCl2, thermal ellipsoids at the 50 % probability level.
Mentions: The 4-coordinate quinolato-chloroborane precursors are afforded by mixing the chloroborane withQOSiMe3 (Scheme 3), followed bywashing with pentane to remove any unreacted BCl3/RBCl2 and/orQOSiMe3. The final step en route to borenium formation is abstraction of thechloride ligand with aluminium trichloride concomitantly forming the tetrachloroaluminate counterion(Scheme 4). In previous studies this anion has been shown tobe both stable and weakly coordinating towards highly electrophilic borenium centres unlike otherclassic weakly coordinating anions (WCA).13 However, afeature of the quinolato architecture is the presence, even when coordinated to boron, of a mildlyLewis basic site at oxygen that complicates the reactivity with AlCl3.

Bottom Line: All the prepared borenium cations are highly chlorophilic and exhibit significant interaction with AlCl4(-) resulting in an equilibrium concentration of Lewis acidic "AlCl3" species.In contrast, QOBPh(+) and QOBTh(+) systems effect the syn-1,2-carboboration of 3-hexyne.DFT calculations at the M06-2X/6-311G(d,p)/PCM(DCM) level confirm that the higher migratory aptitude of Ph versus Me leads to a lower barrier to 1,2-carboboration relative to 1,1-carboboration.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL (UK).

No MeSH data available.