Pher G. Andersson

Modern reduction methods

REDUCTIONS OF CARBONYLES Hydrogenation Transfer-Hydrogenation Metal Hydrides Hydroboration Hydrosilylation Enzymatic REDUCTIONS OF ALKENES Hydrogenation Hydroboration Hydroalumination Hydrosilylation Organocatalysis REDUCTIONS OF IMINES Hydrogenation Transfer-Hydrogenation Hydroboration Hydrosilylation Organocatalysis Bronsted Lewis Base REDUCTIONS OF ALKYNES Hydrogenation Hydroboration Hydrosilylation Hydroalumination REDUCTIVE AMINATIONS Organocatalysis Boranes REDUCTIVE CROSS COUPLINGS Imines and Aldehydes REDUCTIVE HECK COUPLINGS REDUCTIVE COUPLINGS Beta-lactams NA-NAPHTHALENE KINETIC RESOLUTIONS HYDROGENOLYSIS

Asymmetric Hydrogenation of Olefins Using Chiral Crabtree-type Catalysts : Scope and Limitations

Asymmetric Hydrogenation of Olefins Using Chiral Crabtree-type Catalysts : Scope and Limitations

Pyranoside phosphite-oxazoline ligands for the highly versatile and enantioselective ir-catalyzed hydrogenation of minimally functionalized olefins. A combined theoretical and experimental study.

A modular set of phosphite-oxazoline (P,N) ligands has been applied to the title reaction. Excellent ligands have been identified for a range of substrates, including previously challenging terminally disubstituted olefins, where we now have reached enantioselectivities of 99% for a range of substrates. The selectivity is best for minimally functionalized substrates with at least a moderate size difference between geminal groups. A DFT study has allowed identification of the preferred pathway. Computational prediction of enantioselectivities gave very good accuracy.

Remote Dipole Effects as a Means to Accelerate [Ru(amino alcohol)]-Catalyzed Transfer Hydrogenation of Ketones

A new generation of 2-aza-norbornyl amino alcohol ligands for the catalytic transfer hydrogenation reaction of aromatic ketones was synthesized. Extremely active catalysts were formed by introducing a ketal functionality at the rear end of the ligand. Acetophenone was reduced in 96% ee at low catalyst loading, substrate to catalyst ratio, S/C 5000, within 90 minutes with isopropyl alcohol as the hydrogen donor. It was found that the dioxolane substituent in the ligand increased the turnover frequency, TOF50, from 1050 h(-1) to 3000 h(-1) at an S/C ratio of 1000. Introduction of a methyl group at the carbinol carbon resulted in TOF50 as high as 8500 h(-1). Transfer hydrogenation of a range of aromatic ketones was evaluated and found to reach completion within 30 minutes at room temperature, and excellent enantioselectivity, up to 99 % ee, was obtained. A possible explanation for the enhanced activity was provided by density functional calculations, which showed that the presence of a remote dipole in the ligand lowered the transition state energy.

Chiral Pyranoside Phosphite-Oxazolines : A New Class of Ligand for Asymmetric Catalytic Hydrogenation of Alkenes

We have described the first successful application of a phosphite-oxazoline ligand library in the asymmetric Ir-catalyzed hydrogenation of several unfunctionalized olefins. The introduction of a bulky biaryl phosphite moiety in the ligand design is highly adventitious in the product outcome. By carefully selecting the ligand components, we obtained high activities (TOFs up to >1500 mol x (mol x h)(-1) at 1 bar of H2) and enantioselectivities (ee values up to >99%) and, at the same time, show a broad scope for different substrate types. So, this is an exceptional ligand class that competes favorably with a few other ligand series that also provide high ee values for tri- and disubstituted substrate types.

Iridium Phosphite−Oxazoline Catalysts for the Highly Enantioselective Hydrogenation of Terminal Alkenes

A modular library of readily available phosphite-oxazoline ligands (L1-L16a-f) has been successfully applied for the first time in the Ir-catalyzed asymmetric hydrogenation of a broad range of highly unfunctionalized 1,1,-disubstituted terminal alkenes. Enantioselectivities up to >99% and full conversions were obtained in several 1,1-disubstituted alkenes, including substrate classes that have never been asymmetrically hydrogenated before (i.e., 1,1-heteoraryl-alkyl, 1,1-diaryl, trifluoromethyl, etc.). The results indicated that these catalytic systems have high tolerance to the steric and electronic requirements of the substrate and also to the presence of a neighboring polar group. The asymmetric hydrogenations were also performed using propylene carbonate as solvent, which allowed the Ir catalyst to be reused and maintained the excellent enantioselectivities.

Preparation and evaluation of nitrene precursors (PhI=NSO2Ar) for the copper-catalyzed aziridination of olefins

The preparation of different [N-(arenesulfonyl)imino]phenyliodinanes is described along with an evaluation of their utility as nitrene precursors for the copper-catalyzed aziridination of different ...

Combined Experimental and Theoretical Study of the Mechanism and Enantioselectivity of Palladium- Catalyzed Intermolecular Heck Coupling

The asymmetric Heck reaction using P,N-ligands has been studied by a combination of theoretical and experimental methods. The reaction follows Halpern-style selectivity; that is, the major isomer is produced from the least favored form of the pre-insertion intermediate. The initially formed Ph-Pd(P,N) species prefers a geometry with the phenyl trans to N. However, the alternative form, with Ph trans to P, is much less stable but much more reactive. In the preferred transition state, the phenyl moiety is trans to P, but significant electron density has been transferred to the alkene carbon trans to N. The steric interactions in this transition state fully account for the enantioselectivity observed with the ligands studied. The calculations also predict relative reactivity and nonlinear mixing effects for the investigated ligands; these predictions are fully validated by experimental testing. Finally, the low conversion observed with some catalysts was found to be caused by inactivation due to weak binding of the ligand to Pd(0). Adding monodentate PPh3 alleviated the precipitation problem without deteriorating the enantioselectivity and led to one of the most effective catalytic systems to date.

Room temperature and solvent-free iridium-catalyzed selective alkylation of anilines with alcohols

A bidentate iridium NHC-phosphine complex has been developed and applied to the N-monoalkylation of aromatic amines with a wide range of primary alcohols and to the N-heterocyclization of amino alcohols. This reaction resulted in high isolated product yields, even at room temperature and under solvent-free conditions.

PALLADIUM(II)-CATALYZED CYCLIZATION USING MOLECULAR OXYGEN AS REOXIDANT

Abstract A Palladium(II)-catalyzed intramolecular allylic oxidation using nitrogen and oxygen nucleophiles and molecular oxygen as reoxidant has been developed.