Dialkoxy Disulfides Research Articles

Chemical shift and coupling constant analysis of dibenzyloxy disulfides

Dialkoxy disulfides have found applications in the realm of organic synthesis as an S2 or alkoxy donor, under thermal and photolytic decompositions conditions, respectively. Spectrally, dibenzyloxy disulfides possess an ABq in the 1H NMR, which can shift by over 1.1ppm depending on the substituents present on the aromatic ring, as well as the solvent employed. The effect of the said substituents and solvent were analyzed and compared to the center of the ABq, geminal coupling, and the differences in chemical shifts of the individual doublets. Additionally, quantum-chemical calculations demonstrated the intramolecular H-bonding arrangement, found within the dibenzyloxy disulfides.

Thermochemical properties of dibenzyloxy disulfides

The in situ thermal behavior of dialkoxy disulfides (OSSO) has been previously explored, however their neat thermal stability has yet to be examined. We synthesized a library of ten dibenzyloxy disulfide derivatives with various para-substituents. Each derivative was analyzed by TGA and DSC to discern molecular fragmentation. A correlation of the pattern of fragmentation to Swain and Lupton's R-value was observed. Also, DSC analysis revealed that when the para-substituent was a phenyl (i.e. bis(p-phenylbenzyloxy) disulfide), and successive runs were performed, the thermogram showed the presence of the fragmentation, and upon 1H NMR analysis its corresponding alcohol and aldehyde were observed.

Thermochemical properties of iodinated cubane derivatives

Since the initial synthesis of cubane, numerous derivatives have been made with a diverse range of physical, chemical, and biological properties. Some iodinated cubane derivatives have been reported to be thermolytically unstable and/or rearrange in situ. An iodinated cubane-containing, norbornene-based polymer showed rapid thermo-decomposition during TGA studies. Bis-(4-iodocubylmethyl)-dialkoxy disulfide undergoes fragmentation more easily than its non-iodinated counterpart. The synthesis and thermal behaviour of a library of iodinated cubane compounds are herein reported. Most of the iodinated cubane derivatives showed melting/decomposition with no exotherm upon cooling. 4-Iodo-1-vinylcubane was observed to rearrange to 4-vinyl-trans-β-iodostyrene and its cyclooctatetraene intermediate during DSC analysis. TGA studies on 1-iodo-4-(hydroxymethyl)-cubane suggest that this particular iodinated cubane scaffold is mostly prone to rapid thermo-decomposition.

Thermolytic decomposition of benzylic dialkoxy disulfides

Dialkoxy disulfides have been used as an alkoxy radical source under photolytic conditions. In addition, this class of disulfide thermally decomposes to deliver S 2 to dienes. We examined benzylic dialkoxy disulfides (X–Ph–CH 2–O–S–S–O–CH 2–Ph–X) under thermolytic conditions and observed that the rates of decomposition are related to Swain and Lupton’s field constant, F . In addition, the observed non 1:1 ratio of alcohol to aldehyde reaffirms Harpp’s-postulated cage mechanism. We have shown that the ratio is dependant upon the substituent present which can enhance the pi-stacking ability with the solvent, and thus favor diffusion out of the solvation cage yielding the non 1:1 ratio observed.

Photolytic, autocatalyzed decomposition of benzylic dialkoxy disulfides

The dialkoxy disulfide moiety has been shown to go through an intramolecular fragmentation to liberate trappable S 2, and can yield an alkoxy radical under photolytic conditions. We have examined a family of benzylic dialkoxy disulfides (X–Ph–CH 2–O–S–S–O–CH 2–Ph–X) under photolytic conditions and observed a correlation of decomposition based upon the substituent. We have been able to show that the decomposition is autocatalyzed and has a parabolic correlation with Swain and Lupton’s field constant, F .

Disulfur Dichloride (S2Cl2)

Disulfur dichloride (S2Cl2), also known as sulfur chloride (SCl), is widely used in organic synthesis as a sulfurizing and chlorinating agent. Sulfide compounds are found in many natural products and may have useful biological properties. [1] This reagent has been explored for the preparation of heteroaryl disulfides, [2] symmetric aryl di-, tri-, and tetrasulfides, [2] [3] episulfides [4] and benzopolysulfides. [5] [6] Moreover, S2Cl2 is a suitable substrate for the synthesis of dialkoxy disulfide, [7] or for the Herz reaction. [8] It decomposes into SO2, HCl, and S8 when exposed to wet air due to reaction with water.

Fascinating organosulfur functionalities: Polychalcogens as diatomic sulfur sources

AbstractRecent work on the chemistry of dialkoxy disulfides is summarized. It includes various aspects of their structure and relationship to the isomeric thionosulfites as well as their use as diatomic sulfur precursors. © 2007 Wiley Periodicals, Inc. 18:449–459, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20341

Investigation of Sulfur Extrusion from a Cyclic Dialkoxy Disulfide

The relationship of cyclic dialkoxy disulfide 11, its thionosulfite isomer 12, and the related sulfoxylate 13 has been examined. Investigations demonstrate an interconversion between thionosulfite 12 and sulfoxylate 13. This sequential transformation brings evidence that a branched-bond sulfur structure is likely involved in sulfur extrusion.

Synthesis of New Cyclic Dialkoxy Disulfides

Five new cyclic dialkoxy disulfides have been synthesized and fully characterized. An X-ray structure was obtained for the 2,3-furandimethylene dialkoxy disulfide.

Crossover Point between Dialkoxy Disulfides (ROSSOR) and Thionosulfites ((RO)2SS): Prediction, Synthesis, and Structure

Isomeric preference between cyclic dialkoxy disulfides and thionosulfites is governed by the ring size of the heterocycle. Rings smaller than seven atoms prefer the thionosulfite connectivity, whereas larger rings or acyclic analogues favor the unbranched dialkoxy disulfide structure. Density functional calculations were employed to predict the crossover point at which both constitutional isomers are of comparable stability. Follow-up synthesis provides the previously unknown eight-membered ring dialkoxy disulfide 14 and seven-membered ring thionosulfite 15 from the same reaction. X-ray crystallography for all but one of the reaction products and complementary NMR analysis furnishes insights into both solid-state and solution conformations. A long-standing issue regarding the concerted vs catalyzed isomerization pathway between XSSX and X(2)S=S has been addressed for X = RO and shown to be acid dependent.

Generalized Synthesis and Physical Properties of Dialkoxy Disulfides

A substrate study was undertaken in order to probe the scope of S(2)Cl(2) coupling of alcohols to form dialkoxy disulfides. Compounds 1b and 1f are new; along with 1a, 1c, 1h, and 1j, all of the title compounds are fully characterized, and the yields of 1a and 1c have been optimized from previously reported syntheses. The effect of the R-substituent about the OSSO moiety has been carefully probed as yields vary. A substrate and a solvent study of the coalescence behavior of this class was carried out. The origin of the inherently large barrier to rotation and the resultant thermal decomposition pathway is discussed. Both phenomena are shown to be solvent independent; hindered rotation is substrate independent. The decomposition of 1a is ca. 7 kcal/mol higher than the barrier to rotation about the S-S bond. The combined evidence suggests acyclic unsymmetric homolytic cleavage of the dialkoxy disulfide.

Dialkoxy Disulfides and Their Branch‐Bonded Thionosulfite Isomers

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Practical Synthesis of Mixed Allyl and Allenesulfinates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Tandem sigmatropic rearrangements and cyclizations of propargylic dialkoxy disulfides

The first successful preparation of propargylic dialkoxy disulfides in high yields is reported. These esters afforded novel 6,7-dithiabicyclo[3.1.1]heptane-2-one 6-oxide derivatives via an unprecedented sequence of three [2,3]- and one [3,3]-sigmatropic shifts followed by an intramolecular [2+2] cycloaddition. The latter are structurally related to the zwiebelanes, recently isolated from freshly cut onion.

A Practical Synthesis of Mixed Allyl and Allenesulfinates

A new, general, and efficient method for the preparation of mixed sulfoxylates (ROSOR') by treatment of symmetrical dialkoxy disulfides (ROSSOR) with alcohols at room temperature has been found. Subsequent spontaneous [2,3]-sigmatropic rearrangements of mixed sulfoxylates such as alkyl allyl and alkyl propargyl sulfoxylates afford mixed alkyl allyl and alkyl allenesulfinates in good yield. The latter are not readily available by other routes.

Dialkoxy disulfides from cubycarbinols

Two dialkoxy disulfides 2 and 3 have been synthesized in respectable yields. The behaviour of 2 and 3 under thermal and photolytic conditions has been examined and we report the first examples of S 2 liberation from aliphatic dialkoxy disulfides.

Facile preparation and rearrangement of allylic dialkoxy disulfides

Allylic dialkoxy disulfides were obtained in good yields and their reactivity has been investigated. Similarly to allylic sulfoxylates, these esters undergo double [2,3]-sigmatropic rearrangement to the appropriate vic-disulfoxides. The latter, being unstable, undergoes spontaneous rearrangement to the corresponding thiosulfonates.

17O NMR studies on dialkoxy disulfides

17O NMR spectra, at natural isotopic abundance, of dialkoxy disulfides are presented and β- and γ-SCS effects shortly discussed. © 1998 John Wiley & Sons, Ltd.

ChemInform Abstract: Conformational Studies by Dynamic NMR. Part 60. Structure and Stereomutation of the Enantiomers of Dialkoxy Disulfides.

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Conformational Studies by Dynamic NMR. 60.1 Structure and Stereomutation of the Enantiomers of Dialkoxy Disulfides

The structure of dialkoxy disulfides ROSSOR has been established by single-crystal X-ray diffraction of 1, ArCH2OSSOCH2Ar (Ar = 4-nitrophenyl). The gauche conformation (OSSO dihedral angle = 85.4°) observed in the solid state entails the existence of M and P enantiomers that were actually detected in solution, in the case of MeOSSOMe, t-BuOSSOBu-t, and t-BuOSSOMe (3, 4, 5, respectively), by means of NMR spectroscopy in a chiral environment. The activation parameters (ΔG⧧, ΔH⧧, and ΔS⧧) for the stereomutation of this type of enantiomers, brought about by the S−S bond rotation at high temperature (50−110 °C), were measured by computer line shape simulation of the dynamic NMR spectra of appropriate derivatives bearing alkyl substituents with potentially diastereotopic geminal groups. The free energies of activation for such a process (18−19 kcal mol-1, depending on the compound) were found to be much higher than for the corresponding disulfides (RSSR), owing to the larger S−S double-bond character, as indica...