Jacek Skarżewski

Selective oxidation of primary hydroxy groups in prinary-secondary diols

Abstract The two-phase oxidation of primary-secondary diols with sodium hypochlorite, mediated by TEMPO, brings about selective oxidation at the primary position. Such 5 diols are oxidized to the corresponding hydroxyaldehydes.

Vanadium catalyzed enantioselective oxidation of sulfides: easy transformation of bis(arylthio)alkanes into C2 symmetric chiral sulfoxides

Abstract A facile and selective method for the title transformation is described. The two-phase oxidation of bis-sulfides with hydrogen peroxide catalyzed by vanadium complex of chiral Schiff base leads to the corresponding chiral mono- and bis-sulfoxides. In the case of 1,2-bis(arylthio)ethanes the respective optically active bis-sulfoxides are formed in up to over 95% e.e.

Synthesis of C2 symmetric primary vicinal diamines. Double stereospecific mitsunobu reaction on the heterocyclic diols derived from tartaric acid

Abstract Homochiral 1-alkyl-3,4-dihydroxypyrrolidines, ( S , S )- and ( R , R )- 5 were obtained by cyclization and reduction of both enantiomers of (+)- and (−)-tartaric acid, respectively. Also ( S , S )-3,4-dihydroxytetrahydrofurane 6 was prepared from (+)-diethyl tartrate. All these heterocyclic vic -diols underwent twofold Mitsunobu reaction (Ph 3 P/DEAD/HN 3 ) followed by catalytic hydrogenation forming stereospecifically the corresponding primary vicinal diamines ( R , R )-, (S,S)- 2 and (R,R)- 3 . The absolute configuration of diamines 2, 3 was established by the exciton-coupling CD spectra of their N,N′-diphthaloyl derivatives.

Simple preparation of enantiomeric Michael adducts of thiophenol to chalcones: easily available new chiral building blocks

Abstract A facile and enantioselective method for the multigram preparation of the title compounds is described. The Michael addition of thiophenols to chalcones catalyzed by (+)-cinchonine, followed by crystallization, led to the corresponding adducts 2 in up to >95% e.e. The stereoselective Beckmann rearrangement of the oxime of (+)-1,3-diphenyl-3-phenylsulfanylpropan-1-one 2a gives the anilide of (R)-(+)-3-phenyl-3-phenylsulfanylpropanoic acid (as determined by X-ray analysis) and alcoholysis leads to the corresponding enantiomerically pure ethyl ester.

Chiral β-amino sulfoxides. Synthesis, configurational assignment and conformational analysis based on X-ray, CD, 1H NMR and theoretical calculations

Abstract Enantiomerically pure u and l β-amino sulfoxides have been easily obtained from the respective homochiral α-amino alcohols. The absolute configuration at the created stereogenic centre was assigned by CD spectra and by X-ray analysis. Conformational analysis of the title compounds was carried out using quantum chemical energy-geometry optimization. Thus established conformational behavior explained the strongly configuration dependent NMR spectral patterns observed for the u and l diastereomers.

Lipophilic complexones. Part 2 : Synthesis of polyethers derived from 2-alkyl-1, 3-propanediols and 2, 2-bis (hydroxymethyl) decanol

Lipophilic di-, tri-, tetra-, and hexaamines were synthesized from 2-alkyl-1,3-propanediols and 2,2-bis(hydroxymethyl)alkanols. The alcohols were converted into the sulfonate esters which were substituted with ethylenediamine or sodium azide. The azides were directly reduced to give amines. Also dioxyethylenated 2-octadecyl-1,3-propanediol yielded the corresponding amine. Some amines were converted into the salicylidene derivatives.ZusammenfassungLipophile Di-, Tri-, Tetra- und Hexamine wurden aus 2-Alkyl-1,3-Propandiolen und 2,2-Bis(Hydroxymethyl)-alkanolen dargestellt. Die Alkohole wurden in die Sulfonestern übergeführt, welche weiter durch Ethylendiamine oder Natriumazid substituiert wurden. Die Azide wurden direkt zu Aminen reduziert. Aus Di-oxyethylenierten 2-Oktadeka-1,3-propandiolen wurden entsprechende Amine gewonnen. Aus einigen Aminen wurden Salizylidenederivative dargestellt.

Carbon-acylations in the presence of magnesium oxide. A simple synthesis of methanetricarboxylic esters

Abstract Magnesium oxide is an effective reagent for the carbon - acylation of malonates with either acyl chlorides or chloroformates. Various malonic esters (methyl, ethyl, isopropyl and isobutyl) were easily alkoxycarbonylated to give the corresponding methanetricarboxylic esters. The reaction scope and limitations have been elaborated.

A new and efficient route to homochiral γ-hydroxysulfoxides and γ-hydroxysulfones

Abstract Readily available (+)-( R )-1,3-diphenyl-3-phenylsulfanyl-propan-1-one 1 was oxidized to the corresponding sulfone and its reduction gave separable (1 R ,3 R )- and (1 S ,3 R )-1,3-diphenyl-3-phenylsulfonylpropan-1-ols. When 1 was reduced to the mixture of epimeric alcohols, subsequent reaction with three different sulfoxidation agents allowed the separation of all four diastereomeric 1,3-diphenyl-3-phenylsulfinylpropan-1-ols in diastereomerically pure form. The absolute configuration at the newly created stereogenic carbon was proved by chemical correlation, while the configuration of the sulfur centre of the phenylsulfinyl group was established by CD spectroscopy.

Substituted N -salicylidene β-aminoalcohols: preparation and use as chiral ligands in enantioselective sulfoxidation and conjugate addition

A high yielding synthesis of optically active 3,5-disubstituted salicylidene β-amino alcohols (6) is described. The catalytic use of D or L-N-(3-phenyl-5-nitrosalicylidene)valinol in enantioselective sulfoxidation (H2O2 / VO(acac)2) gives up to 95% e.e. Asymmetric conjugate addition of thiophenol to 2-cyclohexen-1-one catalysed by Ti(OPr-i)4 and 6 leads to maximum 31% e.e. in the product.

Diastereoselective Corey–Chaykovsky 9-Epoxymethylation of Cinchona Alkaloids: Access to Chiral Scaffolds with Diverse Functionalities

Reaction of dimethylsulfonium methylide with Cinchona alkaloid ketones proceeds with complete diastereoselectivity to give epoxides of 8,9-like configuration. The reaction of dimethylsulfoxonium methylide gives different isomers, albeit with lower (4:1) selectivity. α-Epimerization of the alkaloid ketones resulted in formation of two separable diasteromeric products. The configurations of the epoxides were elucidated on the basis of NMR data combined with DFT calculations. Models explaining observed selectivity are discussed. The epoxides were efficiently transformed to a number of derivatives through selective S(N)2-type ring-opening reactions with various nucleophiles, often without the need of additional purification steps.