I. Kapovits

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.

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.

Diaryldiacyloxyspirosulfuranes. Part 3. Sulfuranes with five-, six- and seven-membered spirorings: syntheses and molecular structures

Three novel diaryldiacyloxyspirosulfuranes (2–4) with five-, six- and seven-membered spirorings have been prepared, and their molecular structures determined by X-ray diffraction. The structure of spirosulfurane 1 with two identical five-membered spirorings has been reinvestigated. In all spirosulfuranes 1–4 the arrangement of the ligands about the central sulfur atom show a slightly distorted trigonal bipyramidal (TBP) geometry resulting in chiral molecular structure. The axial (hypervalent) S–O and equatorial (covalent) S–Car bond lengths range from 1.838(1) to 1.872(3) and from 1.771 (3) to 1.794(4)A, respectively. The axial O–S–O and equatorial Car–S–Car bond angles lie in the narrow intervals of 174.9(2)–177.4(4)° and 105.8(2)–106.9(2)°, respectively. The five-membered spirorings are practically planar in 1–3. The six-membered spirorings in 2 and 4 assume distorted sofa conformations. The seven-membered spiroring in 3, having four Car atoms with planar configuration, is irregular. The aromatic rings fused with the spirorings are perpendicular to the equatorial plane only if the spiroring is five-membered. In other cases the stable conformations with TBP geometry about sulfur involve a significant torsion of the aromatic ring about the S–Car axis. Thus, in diaryldiacyloxyspirosulfuranes having acyloxy-O ligands at axial positions the structural parameters about the sulfur are not considerably influenced by the shape and size of the spirorings. The O–S–O moiety with hypervalent bonds may be regarded as a structural unity. The sum of the individual S–O bond lengths, (3.684–3.744 A) which is characteristic of diaryldiacyloxyspirosulfuranes, differs markedly from the values found earlier for dialkoxy- and acyloxy-alkyloxy analogues (3.601 and 3.910 A, respectively). For spirosulfurane 3 a rearrangement into the isomeric ten-membered cyclic anhydride 13 is observed.

Conformation of diaryl sulphides with intramolecular sulphur(II)—oxygen interaction: an X-ray study of methyl 2-(4-nitrophenylthio)benzoate and 2-diazoacethyl-4′-nitrodiphenyl sulphide

Abstract The molecular structures of methyl 2-(4-nitrophenylthio)benzoate and 2-diazoacetyl-4′-nitrodiphenyl sulphide have been determined by X-ray diffraction. The skew conformation observed for the ester is favourable to the formation of a sulphur(II)—oxygen(carbonyl) close contact, but unfavourable to sulphur(II)—aryl(nitro) conjugation, as shown by S(II)⋯O (2.701 A) and S(II)⋯C ar (nitro) (1.780 A) distances. For the diazo compound exhibiting a distorted twist conformation S(II)…O (2.778 A) and S(II)C ar (nitro) (1.765 A) were measured. In the latter case, the extremely long CO distance (1.234 A) and the very low ν(CO) frequency (1600 cm −1 ) may be due to both the enolate structure of the COCHN 2 group, and the donor—acceptor interaction between carbonyl—oxygen and sulphur(II) atoms. NoS(II)⋯C −C (diazomethyl) close contact was observed.