Jörg Wilken

Diastereoselective synthesis of vinylmorpholines by palladium-catalyzed tandem allylic substitutions using enantiopure aminoalcohols as bifunctional nucleophiles

Abstract Enantiopure vinylmorpholines have been prepared by a diastereoselective disubstitution ( de up to 92%) of (Z) ROCH 2 CHCHCH 2 OR (R = Ac, CO 2 Me) by aminoalcohols in the presence of palladium catalysts.

Enantioselective catalytic reduction of acetophenone with borane in the presence of cyclic α-amino acids and their corresponding β-amino alcohols

Abstract The direct application of α-amino acids as chiral auxiliaries in the enantioselective catalytic reduction of acetophenone with borane in refluxing toluene has been investigated. A comparison with the corresponding β-amino alcohols as optically active catalysts is involved.

Tetra-tert-butylpyrazole and tetra-tert-butylthiophene

Abstract Tetra- tert .butylpyrazole ( 4 ) and tetra- tert .butylthiophene ( 11 ) were prepared starting from the seven membered cycloalkyne 1 and a reductive desulfurization in the last step. Some reactions of 4 and 11 are described. X-ray structural analyses of 11 and the corresponding S,S-dioxide were carried out.

Palladium-mediated enantioselective formation of 2-methyltetral-1-one from the corresponding allyl or benzyl enol carbonate in the presence of enantiopure aminoalcohols

Abstract The palladium-induced cleavage at room temperature of (2-methyl-1-tetralenyl) benzyl carbonate under bubbling of hydrogen led to (R) 2-methyltetral-1-one with 90% chemical yield and 64% enantiomeric excess in the presence of catalytic amounts of (+) endo-2-hydroxy-endo-3-aminobornane.

Synthesis and application of C2-symmetrical bis-β-amino alcohols based on the octahydro-cyclopenta[b]pyrrole system in the catalytic enantioselective addition of diethylzinc to benzaldehyde

Abstract Asymmetric catalytic ethylation of benzaldehyde utilizing a series of new, tetradental bis-β-amino alcohols based on the octahydro-cyclopenta[ b ]pyrrole system—derived from an industrial waste material—is presented. Attention is focused on steric aspects of the catalyst(-precursor) structure. Furthermore, the catalytic efficiency of the ethylene-bridged, C 2 -symmetrical bis-β-amino alcohols is compared to related ‘monomeric’ structures. Potent chiral ligands, which are highly effective even at concentrations of below 2 mol%, have been developed reaching excellent enantioselectivities up to 100% ee.

Intramolecular vs. intermolecular induction in the diastereoselective catalytic reduction of enantiomerically pure ketones with borane in the presence of cyclic β-amino alcohols

Abstract Asymmetric reduction of various enantiomerically pure ketones was carried out by using oxazaborolidine catalysts with a variety of achiral and chiral ligands. The efficiency of chiral 1,2-amino alcohols as well as the effect of the stereogenic centers in the substrate on the catalytic asymmetric reduction were studied. It was found that the corresponding secondary alcohols were obtained with extremely high stereoselectivities with the proper choice of chiral ligands although a considerably large double asymmetric induction was observed in some cases.

Enantioselective Catalytic Borane Reduction of Prochiral Ketones: Synthesis and Application of New Rigid β-Amino Alcohols with a Cycloalkanol Subunit

Abstract Enantiocontrolled reduction of prochiral ketones with borane in the presence of new enantiomerically pure bi-and tricyclic β-sec-amino alcohols 2–5 as stereodifferentiating catalysts afforded the optically active corresponding secondary alcohols in moderate to excellent (up to 98 % op) optical yields.

Enantioselective synthesis of 1-(1,3-dioxolan-2-yl)-3-pentanol from 3-(1,3-dioxolan-2-yl)-propanal by catalytic ethylation†

Abstract The catalytic enantioselective ethylation of 3-(1,3-dioxolan-2-yl)-propanal by diethylzinc in the presence of various β-aminoalcohol precatalysts is presented. The enantiocontrolled alkylation step was accomplished with enantiomeric ratios of up to 86:14 and chemical yields ranging from 38 to 81% for the resulting 1-(1,3-dioxolan-2-yl)-3-pentanol.

Preparation of an enantiomerically pure helical nickel(II) complex using a new chiral tetradentate ligand derived from an industrial waste material

A new tetradentate ligand (all-R)-1,2-bis(2-aza-3-carboxybicyclo[3.3.0]octan-2-yl)ethane (H2baboc) derived from an industrial waste material has been used as an asymmetric complexing agent for the transition metal nickel(II). The enantiomerically pure complex [Ni(baboc)(H2O)]·H2O has been prepared and its crystal structure has been determined by X-ray diffraction. According to the τ criterion the pentagonal co-ordination sphere for NiII is identified as square pyramidal.

Stereoselektive Pudovik-Reaktion von 5,6-Benzo-2//-l-methyl-3- (2’-chlorethyl)-2-oxo-1,3,2λ4-diazaphosphorin-4-on mit einem 3-Thiazolin und MPL-chromatographische Isolierung des Überschußdiastereomers / Stereoselective Pudovik Reaction of 5,6-Benzo-2H-1-methyl-3-(2’-chloroethyl)-2-oxo-1,3,2λ4-diazaphosphorin-4-one with a 3-Thiazoline and MPL-Chromatographical Isolation of the Major Diastereomer

The modified Pudovik reaction of 5,6-benzo-2H-1-methyl-3-(2′-chloroethyl)-2-oxo-1,3,2λ4-diazaphosphorin-4-one with a 3-thiazoline furnishing the corresponding 5,6-benzo-2H-1-methyl- 3-(2′-chloroethyl)-2-oxo-2-(3-thiazolidin-4-yl)-1,3,2λ4-diazaphosphorin-4-one 4 and the medium pressure liquid column chromatographical (MPLC) isolation of the major diastereomer is described. The relative stereochemistry at the centres PI and Cl was determined by X-ray structure determ ination of three racemic modifications (a total of seven independent molecules).