Árpád Kucsman

Intramolecular sulphur(IV)-oxygen interaction in sulphoxides and sulphilimines with 2-methoxycarbonyl-phenyl and 2-nitrophenyl groups: an X-ray study

Abstract The molecular structures of methyl 2-(methylthio)benzoate, dimethyl 2,2′-dithiodibenzoate, dimethyl 2,2′-thiodibenzoate, methyl 2-(2-nitrophenylthio)benzoate, 2,2′-dinitrodiphenyl sulphide and methyl 2-(2-nitrophenylthio)phenylacetate exhibiting S(II)⋯O(carbonyl) or S(II)⋯O—(nitro) close contact have been investigated by X-ray diffreaction. Planar (ArSMe), equatorial (Ar 2 S 2 ) and skew (Ar 2 S) conformations are explained by steric and conjugative effects and sulphur(II)—oxygen interaction. Linear and non-linear X—S⋯O close contacts resulting from favourable “bond direction” and unfavouralbe “lone-pair direction” approaches (2.619–2.722 and 2.900–3.402 A, respectively) are discussed in detail. Possible aryl ring positions, the geometry of rings with S⋯O contact and the nature of counter-atom (X = C, S) are considered as decisive factors. The results are consistent with different neighbouring group effects found earlier for o -CO 2 Me, o -CH 2 CO 2 Me and o -NO 2 groups. Data support the mutual dependence of S—S and S⋯O distances in compounds with a linear S—S⋯O arrangement. Other bond lenghts, e.g. CO, NO and S(II)—C ar are not affected significantly by sulphur—oxygen interaction.

Intramolecular sulphur—oxygen interaction in organosulphur compounds with different sulphur valence state: an X-ray study of methyl-2-nitrobenzene-sulphenate, -sulphinate, -sulphonate and 2-nitrobenzenesulphenyl chloride

Abstract Molecular structures of methyl-2-nitrobenzenesulphenate, methyl-2-nitrobenzenesulphinate, methyl-2-nitrobenzenesulphonate and 2-nitrobenzenesulphenyl chloride have been determined by X-ray diffraction. The remarkably short S⋯O (nitro) distances (2.458, 2.743, 2.956 and 2.379/2.408 A) found in the almost linear XS⋯O sequences are controlled characteristically by both the valence state of sulphur and the electronegativity of the X counter-atom (X = OMe, O, OMe and Cl, respectively). The structure of the sulphonate is compared with that of the analogous sulphonyl chloride and conformations around the S(VI)C ar bonds are discussed. In the crystal lattice of 2-nitrobenzenesulphenyl chloride, intermolecular S⋯Cl close contacts of two different types (3.447 and 3.452 A) were observed. The differences in the geometries of adjacent molecules may be associated with these interactions.

Diaryldiacyloxyspirosulfuranes—I : Syntheses from sulfides with halogenating agents

Abstract A series of diaryldiacyloxyspirosulfuranes has been prepared from bis(2-carboxyaryl) sulfides with different halogenating agents. In pyridine, sulfides with two electron-withdrawing nitro groups cannot be converted into spirosulfuranes, suggesting the participation of pyridine in Cl+-transfer reactions. UV and IR spectroscopic data for spirosulfuranes are also reported and briefly discussed.

Neighbouring group participation in reactions of sulphides with chloramine-t

Abstract Neighbouring group participation in reactions of chloramine-T with ortho -substituted aryl methyl sulphides and diaryl sulphides has been studied. The reaction is markedly hindered by the steric effect of the ortho substituent of the phenyl ring, but groups having a CO moiety show an anchimeric effect in the following order: o -CH 2 CO 2 Me ~ o -CH 2 CO 2 H o -CH 2 CO 2 - o -CO 2 Me ~ o -CO 2 H o -CO 2 - ⪡ 2o-CO 2 in the rate-determining step may be ruled out on the basis of salt and isotope effect. Substituents with neighbouring group participation diminish the yield of sulphilimine in solvents containing water. The electrophilic chlorination of sulphides by TsNHCl may be assumed to be the rate-determining step with the positively charged sulphonium centre stabilized by the negatively polarized or charged carbonyl-oxygen in the transition state. This type of interaction hinders the nucleophilic attack of sulphonamidate ion at the sulphonium centre in the fast product-controlling steps, decreasing the yield of sulphilimine.

Spirosulfuranes with different heteroatoms in axial positions A comparison of NS(IV)O and NS+(IV)⋰O systems

Abstract Three novel spirosulfuranes with N and O heteroatoms in axial positions and with five- and six-membered spirorings ( 4–6 ), as well as the molecular complex of the dipolar ion 7 with methanol, have been prepared and their molecular structures determined by X-ray diffraction. The molecular structures of the spirosulfuranes 4–6 show slightly distorted geometries, while that of the dipolar ion 7 is considerably distorted about the central sulfur. The axial interatomic distances for SN and SO in 4–6 range from 1.71 to 1.74 A and from 2.13 to 2.225 A, respectively (1.69 and 2.60 A for 7 ). The axial NSO and the equatorial C ar SC ar angles lie in the intervals 174–179° and 104–105°, respectively, for the spirosulfuranes 4–6 (157 and 104° for 7 ). The SC r bond lengths in all of the compounds investigated are similar to those given for typical S(IV)C ar bonds (1.76–1.82 A). A comparison is also presented between the structural parameters of the spirosulfurances 4–6 and those of the cyclic sulfonium salts 1a–3 and of the molecular complex 7 with analogous structures to the spirosulfuranes studied. The conformations for all of the model compounds as well as for the sulfoxide 8 and sulfide 9 related to the spirosulfuranes and sulfonium salts investigated are also discussed.

Über den mechanismus der sulfilimin-bildung—II : Die reaktion von thioäthercarbonsäuren mit Chloramin-T

Resume Bei der Einwirkung von Chloramin-T auf Thioather verlauft neben der Sulfilimin-Bildung auch eine Oxydation, die bei einigen Thioathercarbonsauren stark in den Vordegrund tritt. Es wurde gefunden, dass der Beteiligungsanteil der beiden Reaktionen mit der Struktur der Thio-athercarbonsauren eng zusammenhangt, indem die Oxydationsreaktion durch die raumliche Nahe der Carboxylatgruppe zum Schwefelatom stark gefordert wird; ist dies nicht der Fall, so wird die Bildung des Sulfilimins begunstigt. Die Ursache dieses Zusammenhanges wird theoretisch begrundet.

Intramolecular sulfur—oxygen interaction: An ab initio conformational study of (Z)-3-fluorothio-2-propenal

Different conformations of (Z)-3-fluorothio-2-propenal, a simple model of compounds exhibiting intramolecular sulfur—oxygen interaction of 1,5 type, have been studied by the ab initio SCF—MO method. The critical points of the relaxed conformational potential energy surface have been obtained with STO-3G optimized geometries and compared to those of a rigid surface. The antiperiplanar—synperiplanar (ap—sp) conformation with S⋯O close contact is found to be the most favourable. As calculated by STO-3G, STO-3G* and 6–31G* basis sets, the preferred ap—sp and ap—ap conformations differ in energy by 1.2, 3.8 and 6.5 kcal mol−1, respectively. In accordance with known experimental rules about sulfur—oxygen interaction, the calculated FS⋯O angle (169.6°) is nearly linear. The S⋯O nonbonded distance (2.852 A), as in most α,β-enone structures, is not extremely short. Bond lengths and bond angles do not differ significantly in the minimum energy conformations with or without S⋯O close contact. In the case of (Z)-3-fluorothio-2-propenal the sulfur—oxygen interaction can be rationalized qualitatively by electrostatic effects of dipolar character between FS and OC moieties.

Stereochemistry of sulphilimine and sulphoxide formations in reactions of sulphides with chlorinating agents and nucleophiles

Abstract The stereochemistry of sulphilimine and sulphoxide formations was studied in reactions of chiral alkyl aryl sulphides either with N-chloro toluenesulphonamides or with t -BuOCl followed by TsNH − Na + both leading to unequal amounts of diastereomers of products. Configurations were determined by spectroscopic methods and stereospecific reactions, and diastereomeric product distributions were measured by hplc. Results are discussed and reaction pathways are suggested for the product-controlling steps. From sulphonium type intermediates sulphoxides are formed by hydrolysis with inversion, while sulphilimines with retention or inversion of configuration at sulphur depending on manner of attack by N-nucleophile. In reactions of ortho -carboxy-substituted sulphides both sulphilimines and sulphoxides are formed from cyclic acyloxysulphonium intermediates with inversion of configuration at sulphur.

Über den mechanismus der sulfilimin-bildung—I : Die reaktion substituierter methylarylsulfide und diarylsulfide mit chloramin-t.

Resume Die Sulfilimin- Bildung der Thioather ist als eine nucleophile Susbstitution der Chloramine zu betrachten. Dafur spricht die Beobachtung, dass die Neigung der Thioather zur Sulfilimin-Bildung mit der Elektronendichte am Schwefelatom ansteigt. Dies liess sich durch Vergleich der Versuchsergebnisse beweisen, die bei der Umsetzung von Chloramin-T mit elektronenanziehende, bzw.elektronensendende Substituenten enthaltenden Methylarylsulfiden und Diarylsulfiden gewonnen wurden

Stereospecific synthesis and absolute configuration of optically active diaryl(acyloxy)(alkoxy)spiro-λ4-sulfanes

Abstract Optically active (R)-(+)-1,1′-spirobi[3H-2,1-benzoxathiol]-3-one (R)-(+)- 5 , the (R)-(+) and (S)-(−) enantiomers of spiro[3H-2,1-benzoxathiol-1,1′-naphtho[1,8-d,e]-3H-2,1-oxathiin-3-one] (R)-(+)- 8 and (S)-(−)- 8 , and (S)-(+)-spiro[3H-2,1-benzoxathiol-3-one-1,1′-naphtho[1,8-d,e]-3H-2,1-oxathiine] (S)-(+)- 10 all belonging to the class of diaryl(acyloxy)-(alkoxy)spiro-λ4-sulfanes (spirosulfuranes) were prepared by dehydration of the optically active diaryl sulfoxides (R)-(+)- 4 , (R)-(+)- 7 , and (S)-(+)- 9 , respectively, all of them carrying reactive CH2OH and COOH substituents. (R)-(+)-5H,7H-dibenzo[c,f]-1,5-oxathiocin-5-one 12-oxide (R)-(+)- 6 , a sulfoxide-lactone isomer of spiro-λ4-sulfane (R)-(+)- 5 was also obtained from (R)-(+)- 4 by dehydration. The molecular structures including the absolute configurations were determined for (R)-(+)- 5 , (R)-(+)- 6 and (R)-(+)- 8 by X-ray diffraction method. Relevant bond length and angle data are listed. Sulfur configurations, solid-state conformations and a stereospecific pathway for the dehydration of sulfoxides are discussed in detail.