The first example of atropisomeric amide-derived P,O-ligands used for an asymmetric Heck reaction

Organocatalytic Asymmetric Synthesis of C-N Atropisomers with Pyrrole, Oxindole and Succinimide Scaffold

An asymmetric synthesis of C-N atropisomers with pyrrole, oxindole and succinimide moities was developed via organocatalytic desymmetric Michael addition of 3-pyrrolyloxindole with prochiral N-aryl maleimides. The C-N atropisomers were obtained in acceptable yields with high diastero- and enantioselectivities (>20 : 1 dr, up to >99 % ee). C-N Rotational energy barrier has also been determined.

Regioselective Heck reaction catalyzed by Pd nanoparticles immobilized on DNA-modified MWCNTs

This is the first report of regioselective Heck reaction of aryl iodides with 2,3-dihydrofuran using heterogonous nanocatalyst.

Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction

A novel class of chiral phosphanyl-oxazoline (PHOX) ligands with a conformationally rigid cyclopropyl backbone was synthesized and tested in the intermolecular asymmetric Heck reaction. Mechanistic modelling and crystallographic studies were used to predict the optimal ligand structure and helped to design a very efficient and highly selective catalytic system. Employment of the optimized ligands in the asymmetric arylation of cyclic olefins allowed for achieving high enantioselectivities and significantly suppressing product isomerization. Factors affecting the selectivity and the rate of the isomerization were identified. It was shown that the nature of this isomerization is different from that demonstrated previously using chiral diphosphine ligands.

Non-Biaryl Atropisomers in Organocatalysis

A new class of 6'-hydroxy cinchona alkaloids, with a non-biaryl atropisomeric functionalisation at position 5' of the quinoline core can be prepared by an easy amination procedure. These are the first derivatives for which the principle of atropisomerism is engrafted in the classical core of the cinchona alkaloids. The aminated cinchona alkaloids are effective organocatalysts for the Michael addition of beta-keto esters to acrolein and methyl vinyl ketone, in up to 93 % ee (ee=enantiomeric excess), as well as for the asymmetric Friedel-Crafts amination of a variety of 2-naphthols, permitting the preparation of the latter in up to 98 % ee. The aminated 8-amino-2-naphthol itself is the first chiral organocatalyst based on non-biaryl atropisomerism. The two enantiomers of this chiral primary amine can be used for the direct alpha-fluorination of alpha-branched aldehydes. The fluorinated compounds can thereby be accessed in up to 90 % ee.

Structure and reactivity of new phosphine ligands containing the hemi-labile sulfone moiety

New heterofunctional phosphine ligands have been synthesised, incorporating the substitutionally labile sulfone and sulfonamide moieties as chelating groups, which display activity in the palladium-catalysed Suzuki and amination cross-coupling reactions. Single-crystal X-ray diffraction studies of the complexes formed with [Pd(mu-Cl)(dmba)] (dmba-H = N,N-dimethylbenzylamine) highlight the coordinating nature of these ligands; showing the formation of a bis chelate complex through a six-membered Pd-P-C-C-S-O ring with the sulfonamide class of ligands.

Slow interconversion of enantiomeric conformers or atropisomers of anilide and urea derivatives of 2-substituted anilines

N-Acylated 2-substituted anilines undergo slow Ar-N bond rotation, allowing in some cases isolation of enantiomeric or diastereoisomeric atropisomers and in others the determination of the rate of Ar-N bond rotation by NMR. 2-Iodoanilides bearing a branched N-substituent demonstrate sufficient enantiomeric stability to be resolvable, either by HPLC or by formation of diastereoisomeric lactanilide derivatives. For the first time, the rates of Ar-N rotation in 2-substituted N,N'-diarylureas have been established: they mainly fall in the region of 50-70 kJ mol(-1) with a relatively weak dependence on substituent size.