J. L. Garcia Ruano

Highly diastereoselective diels-alder reaction of optically active 2-p-tolylsulphinyl-2-cycloalkenones with cyclopentadiene

Abstract The Diels-Alder reaction of (S)-2-p-tolylsulphinyl-2-cyclopentenone (and 2-cyclohexenone) with cyclopentadiene, catalized by AlCl3 and AlEtCl2, occurs at room temperature with complete facial diastereoselectivity, but with moderate endo-exo selectivity.

Synthesis and reduction of chiral sulfinyl cyclohexanones

Abstract The reaction of cyclohexanone with (S)-(−)-menthyl-p-toluenesulfinate in the presence of Pr i 2 NMgBr yields a mixture of enantiomerically pure 2-p-tolylsulfinylcyclohexanone diastereoisomers. Their stereoselective reduction to chiral hydroxysulfoxides is also reported.

Stereochemistry of organic sulphur compounds. part 13. Configurational assignment of diastereoisomers of 2-methylsulphinyl-1,2-diphenylethanol and of their O-methyl and O-acetyl derivatives

Abstract The synthesis, isolation and conformational analysis of the diastereomeric 2-methylsulphinyl-1,2-diphenylethanol and of its O -methyl and O -acetyl derivatives are reported. Chemical correlations and the study of the influence of solvent polarity changes on the coupling constants have permitted the configurational assignment. Lanthanide shift reagents have been used also. to this effect. The role of hydrogen bonding in the hydroxysulphoxides has been evaluated in diluted solutions by IR and NMR spectroscopy. A donor-acceptor interaction between oxygen and sulphur has been invoked to explain the differences in conformational behaviour between epimeric sulphoxides at sulphur atom.

Asymmetric Diels-Alder reactions of γ-alkoxy-α-sulfinylbutenolides

Abstract The synthesis of the enantiomerically pure 5-ethoxy-3- p -tolylsulfinyl-2(5H)-furanones ( 2a and 2b ) and the study of their behaviour as dienophiles in asymmetric Diels-Alder reactions with cyclopentadiene are reported. Depending on the reaction conditions, the π-facial selectivity is mainly controlled by the sulfur or C-5 configurations.

Reactions of chiral β-ketosulfoxides with Et2AlCN: Asymmetric synthesis of cyanohydrin derivatives.

Abstract The reaction of chiral p -tolylsulfinylmethyl ketones (R-CO-CH 2 -SOTol, RPh, Et and t -Bu) with Et 2 AlCN, yields almost optically pure sulfinyl cyanohydrins (d.e. ≥ 96%). The reaction was quicker in the presence of ZnCl 2 , but the stereochemical results were identical, The cyanohydrins were transformed into the α-methyl α-hydroxyamides (e.e.-92%) by hydrolysis of the CN group and subsequent hydrogenolysis of the CS bond.

Reactions of chiral 2-p-tolylsulfinycycloalkanones with AlMe3

Abstract The reactions of ( S2 , Rs ) and ( R2 , Rs )-2- p -tolylsulfinylcyclohexanones with AlMe3/ZnClz only yield the cyclohexylmethylcarbinols with R configuration at hydroxylic carbon. The ( R1 , S2 , Rs )-1-methyl-2- p -tolysulfinylcyclopentanol was the only compound obtained in the reaction of Me3Al with both epimeric 2- p -lolysulfinyleyclopentanones. The d.e. of both reactions are higher than 96%.

Stereochemistry of organic sulphur compounds : Part. 17 conformational analysis of some erythro- and threo-thio-derivatives of β-fluorinated and β-oxygenated ethanes

Abstract The synthesis and conformational analysis of 2-fluoro, 2-hydroxy and 2-methoxy thioderivatives (thioethers, sulphoxides, sulphones and sulphonium salts) of 1,2-dimethyl and 1,2-diphenylethanes ( erythro and threo ) are reported. Steric effects in thioethers and electrostatic interactions in sulphonium salts are the main factors determining the stability rotamers. A balance of these factors controls the conformational equilibria in sulphoxides and sulphones. Electronic interactions between the π -aromatic electrons or the unshared β-heteroatomic electrons and the sulphur atom are suggested to explain large differences in rotamer populations induced by changes in the carbon sketelon or in the relative configuration of the sulphinylic sulphur.

Synthesis and conformational analysis of some oxisuran metabolites and their o-methylderivatives

Abstract The synthesis is given of oxisuran (methylsulphinyl methyl-2-pyridyl ketone) and its metabolites and derivatives, whose structures are 2-Py-CO-CH2-SOxCH3 ( X=0,1,2) and 2-Py-CHOR-CH2-SOnCH3(R=H, Me; n=0,1,2). From the results obtained in the reaction of oxisuran with different reducing agents, a new stereochemical pathway is suggested to explain the stereoselectivity observed in the reduction of β-keto-sulphoxides with DIBAL. The conformational analysis of hydroxy and methoxyderivatives is discussed in relation with that previously reported for 2-thioderivatives of 1-phenylethanol and their O-methylderivatives. The configurational assignment of diastereoisomeric sulphoxides is made on the basis of their different conformational behaviour, confirming the assignment deduced from the stereoselectivity observed in the reduction of oxisuran.

Stereochemistry of Organic Sulfur Compounds. Part 20. Conformational Analysis of Aminosulfoxides and Sulfones.

Abstract Synthesis and conformational analysis of 1-phenyl-2-methylsulfinyl-(and -sulfonyl-) ethylamine (and its N -methyl and N , N -dimethylderivatives) are reported. Conformational preferences have been determined by carefully observing the changes of the vicinal coupling constants with protonation in the 1H-nmr spectra. The strongly configuration dependent conformational behavior displayed by sulfoxides is explained in terms of a previously proposed donor-acceptor interaction between nitrogen and sulfur. Conformational equilibria of sulfones are controlled by steric interactions except when nitrogen is protonated in which case a relatively weak electrostatic attraction takes place between the heteroatomic functions.

Conformational analysis of 1-Y, 2-Z-Cyclohexanes ( Y = OH, OMe, F, Cl, Br and I; Z= SMe, SOMe and SO2Me): Study of the Z/Y gauche interactions

Abstract The conformational study of the title compounds is reported. The configurational assignment of the epimeric sulfoxides was based on the relationship between the stereochemistry of the sulfinyl group and the chemical shifts of the neighboring nuclei. The values of the (Z/Y) gaucha interactions have been estimated in different solvents from G0 values measured in low temperature 13C-nmr spectra.