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Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

preprint
submitted on 19.12.2017, 20:04 and posted on 20.12.2017, 15:15 by Haibo Ge, Lei Pan, Piaoping Tang, Ke Yang, Mian Wang, Jianyi Wang, Guigen Li
Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp3 carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp3)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp3)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.

Funding

NSF (CHE-1350541)

History

Topic

  • Organic Synthesis and Reactions

Email Address of Submitting Author

geh@iupui.edu

Institution

Indiana University-Purdue University Indianapolis

Country

USA

ORCID For Submitting Author

0000-0001-6727-4602

Declaration of Conflict of Interest

No conflict to declare

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