TY - JOUR

T1 - Optically active (peptido-carbene)palladium complexes

T2 - Towards true solid-phase combinatorial libraries of transition metal catalysts

AU - Jensen, Jakob F.

AU - Worm-Leonhard, Kasper

AU - Meldal, Morten

PY - 2008/8

Y1 - 2008/8

N2 - This work explores the potential of forming transition metal catalysts by combinatorial solid-phase peptide chemistry to produce catalysts with enzyme-like properties of stereoselectivity, regioselectivity and even substrate selectivity. A series of new functionalised carbene precursors/donors - imidazolium salts - each containing both amino acid and carboxylic acid functionality was synthesised in solution. The readily accessible carbene precursors were incorporated within the backbones of peptides attached to PEGA resin, by standard solid-phase peptide coupling techniques. The synthetic strategy gave easy access to both mono- and didentate ligand systems, providing folded structures around the central transition metal atoms, with different degrees of steric congestion and bite angles. Changing the number of incorporated amino acids between the two carbene donors facilitated variation of the properties of the complexes. Both ligand systems were complexed to palladium(II) by standard base treatment, and the Pd complexes were studied by mass spectrometry and NMR spectroscopy. The monodentate (carbene) palladium complexes were each the product of enolisation of a neighbouring carbonyl group and loss of a proton, followed by coordination of the oxy anion to the palladium atom. The established methods are suitable for the combinatorial synthesis of palladium catalysts on solid support.

AB - This work explores the potential of forming transition metal catalysts by combinatorial solid-phase peptide chemistry to produce catalysts with enzyme-like properties of stereoselectivity, regioselectivity and even substrate selectivity. A series of new functionalised carbene precursors/donors - imidazolium salts - each containing both amino acid and carboxylic acid functionality was synthesised in solution. The readily accessible carbene precursors were incorporated within the backbones of peptides attached to PEGA resin, by standard solid-phase peptide coupling techniques. The synthetic strategy gave easy access to both mono- and didentate ligand systems, providing folded structures around the central transition metal atoms, with different degrees of steric congestion and bite angles. Changing the number of incorporated amino acids between the two carbene donors facilitated variation of the properties of the complexes. Both ligand systems were complexed to palladium(II) by standard base treatment, and the Pd complexes were studied by mass spectrometry and NMR spectroscopy. The monodentate (carbene) palladium complexes were each the product of enolisation of a neighbouring carbonyl group and loss of a proton, followed by coordination of the oxy anion to the palladium atom. The established methods are suitable for the combinatorial synthesis of palladium catalysts on solid support.

KW - Carbenes

KW - Chiral catalysts

KW - Combinatorial chemistry

KW - Palladium catalysts

KW - Solid phases

UR - http://www.scopus.com/inward/record.url?scp=53749104612&partnerID=8YFLogxK

U2 - 10.1002/ejoc.200800234

DO - 10.1002/ejoc.200800234

M3 - Journal article

AN - SCOPUS:53749104612

SP - 3785

EP - 3797

JO - European Journal of Organic Chemistry

JF - European Journal of Organic Chemistry

SN - 1434-193X

IS - 22

ER -