CH Activation Borylation

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C-H Activation Borylation The Holy Grail of
Catalysis
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C-H activation Process where a strong C-H bond
undergoes substitution to produce a weaker C-M
bond. Functionalisation Metal-C bond is replaced
by any bond except C-H. The challenge Finding
ways to selectively form the C-M intermediate
under synthetically useful, mild conditions that
enable functionalisation and catalyst renewal.
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Alternative Approaches
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• 18 Electron Rule

Stable The metal at the centre of the complex
has the noble gas configuration of 18 electrons
in the valence shells. Electrons The total 18 is
achieved by combining the electrons that the
metal already possess with those donated by the
co-ordinating ligands.
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• Direct Borylation of Alkanes Initial Work

Hartwig Science 1997 (277) 211
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• Direct Borylation of Alkanes Initial Work
• Proposed Mechanism

Hartwig Science 1997 (277) 211
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Alkane Borylation Photochemical
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Hartwig Agnew. Chem. Int. Ed 1999 (38) 3391
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• Direct Borylation of Alkanes Thermal

Smith JACS 1999 (121) 7696
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Alkane Borylation
Hartwig Science 2000 (287) 1995
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Hartwig Science 2000 (287) 1996
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Hartwig Science 2000 (287) 1996
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Hartwig JACS 2001 (123) 8422
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• Proposed high-valent Rh(V) and Ir(V) boryl
  complexes as intermediates in these reactions

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Hartwig JACS 2001 (123) 8422
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Hartwig JACS 2001 (123) 8422
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Alkane Borylation
Hartwig JACS 2004 (126) 15334
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Arene Borylation
Hartwig JACS 2002 (124) 390
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Proposed Mechanism Hartwig
Hartwig JACS 2002 (124) 390
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Proposed Mechanism Smith III
Smith Science 2002 (295) 307
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Hetero Arene Borylation
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• Direct Arene Borylation Suzuki Precursors

Smith Science 2002 (295) 305
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• Direct Arene Borylation One Pot Oxidation

Smith JACS 2003 (125) 7792
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Direct Arene Borylation Ligand Studies
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Nishida Adv. Synth. Catal 2004 (346) 1655
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Alkylbenzene Borylation Rh-catalysed
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Alkylbenzene Borylation Pd-catalysed
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Borylation of Sandwich Compounds
Plenio Chem. Commun. 2004 (13) 1508
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Borylation of Porphyrins
Osaku JACS. 2005 (127) 8264
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Conclusions
5g 21.80
5g 151.10
Cost of 1/2Ir(OMe)(cod)22 125 / 250 mg Ir
complexes are highly active catalysts for the
borylation of aromatic C-H bonds, giving good
yields even at room temperature. Rh and Re
complex are highly active catalysts for the
borylation of alkane C-H bonds. C-H activation
borylation provides an efficient, mild
alternative route to classical transmetalation. L
igand choice important in relation to TON of
catalyst and the conditions used. Still in
infancy, but is showing promising direction.