Sulfoxide forms

Pesticide Solvent. The majority of organic fungicides, insecticides, and herbicides (qv) are soluble in DMSO, including such difficult-to-solvate materials as the substituted ureas and carbamates (see Fungicides, agricultural Insect control technology Pesticides). Dimethyl sulfoxide forms cosolvent systems of enhanced solubiUty properties with many solvents (109). 

A-Chlorosuccinimide 1 N NaOH." With this method, the sulfide is oxidized completely to the sulfone, which is cleaved with hydroxide more readily than the sulfoxide formed by periodate oxidation. It has been reported that oxidation of the sulfide leads to oxidation of adenine and gua-nine." However, see the discussion of the TPTE group below. 

Whereas acyclic sulfoxides form complexes with various metal salts, thiirane oxides react with copper(II) chloride or bromide163 in benzene at room temperature to give the thiolsulfonate 146a. In alcoholic solution below 0 °C the major products are sulfinates (149). Similar results are obtained in the reaction of thiirane oxides with ethanesulfinyl chloride163 as summarized in equation 60. 

Sulfoxides form adducts with Lewis acids like SbCls and SnCU [80]. In the case of SsO the crystalline products SsO-SbCh [81] and (SsO)2-SnCl4 [82] have been prepared and characterized by single crystal X-ray diffraction analyses. Reaction of SsO with SbCls in CS2 at 20 °C and subsequent cooling of the solution to -50 °C resulted in orange orthorhombic crystals of SsO-SbCls in 71% yield. These molecules are of Cg symmetry see Fig.6 [81]. 

Sulfur compounds in combination with peroxyl radical acceptors are often used for the efficient break of hydroperoxide [14]. The mechanism of action of these inhibitory mixtures can, however, be more complex, as demonstrated with reference to a pair of 2,6-diphenylphenol and distearyl dithiopropionate [15]. The combined addition of these compounds with concentrations of 0.05% and 0.3%, respectively, results in an extended inhibitory period during the oxidation of PP (up to 3000 h at 413 K). Sulfide (for instance, (3,(3 -diphenylethyl sulfide) or its products not only break down ROOH, but also reduce the phenoxyl radical. Sulfoxide formed in the reaction of the sulfide with ROOH can react with ArO. Thus, the ability of sulfides and their products to reduce phenoxyl radicals can contribute to their synergistic effect. 

An interesting method for the estimation of optical purity of sulfoxides, which consists of the combination of chemical methods with NMR spectroscopy, was elaborated by Mislow and Raban (241). The optical purity is usually determined by the conversion of a mixture of enantiomers into a mixture of diastereomers, the ratio of which may be easily determined by NMR spectroscopy. In contrast to this, Mislow and Raban used as starting material for the synthesis of enantiomeric sulfoxides a diastereomeric mixture of pinacolyl p-toluenesulfinates 210. The ratio of the starting sulfinates 210 was 60.5 39.5, as evidenced by the H NMR spectrum. Since the Grignard reaction occurs with full stereospecificity, the ratio of enantiomers of the sulfoxide formed is expected to be almost identical to that of 210. This corresponds to a calculated optical purity of the sulfoxide of 20%. In this way the specific rotations of other alkyl or aryl p-tolyl sulfoxides can conveniently be determined. 

On reversed-phase HPLC, the sulfones usually appear in an intermediate position between the more hydrophobic t t[CH2-S] peptide and the more polar t t[CH2—SO] sulfoxides, much as seen in the amino acid analysis by oxidation of Met.162 Unlike sulfoxides, once formed, sulfones are resistant to reduction to sulfides or sulfoxides.1[5T Incorporation of the tp[CH2—S] element and its oxidized counterparts into litorin (positions 8-9), a bombesin-like peptide, gives rise to receptor antagonists that are more potent when in the sulfoxide forms than in the sulfone form. 

Fig. S. Conformational modulation of a peptidic structure ( 6) controlled by a redox process [8], The hydrophilic amino acids are in bold face and the sulfoxide form of methionine is denoted by M°. On the left, the tr-helix axial projection on the right, the 0-sheet side-view representation...

A series of [3-carbonyl sulfides was studied as substrates for CPO-catalyzed oxygenation (Scheme 2.16) [238]. The corresponding dialkyl sulfoxides formed quantitatively if R2 is methyl or ethyl, but the yields drop dramatically for larger substituents. The steric control was present also in cyclic derivatives where the cyclohexanone residue results in about a 50% reduction in yield with respect to the smaller cyclopentanone. Surprisingly, the y-butyrolactone produces the sulfoxide in quantitative amounts [239]. A similar result was obtained with benzo[fo]thiophenes as substrates [240]. 

The sulfoxide forms an equilibrium with an other compound, that is trapped with the phosphorus reagent. 

By Methods A and B, isopropyl phenyl sulfoxide was included in crystalline 1 with high ( -enantioselectivity (86 and 87% ee, respectively). Ethyl phenyl sulfoxide formed no inclusion compound by Method A, but the inclusion compound of its (5)-enantiomer was obtained by Method B. The inclusion crystal of (.V)-e(hyl phenyl sulfoxide is isostructural with that of (S)-isopropyl phenyl sulfoxide (Figure 3). As mentioned above, (6>ethyl phenyl sulfoxide was not included by Method A. The lack of one methyl group may make enthalpy (interaction with the inclusion cavity) and entropy disadvantageous in crystal packing to result in no inclusion of ethyl phenyl sulfoxide via Method A. 

The ozonolysis of XXI was straightforward and very high yielding. The indications were that this step could have been carried out at a much higher temperature than the -65°C temperature we used, since the substrate XXI was already in the sulfoxide form. 

Sulfoxides form complexes with hydroperoxides and can inhibit a partially oxidized substrate, but their inhibiting activity is destroyed by the simultaneous addition of an acidic substance such as stearic acid. The "activity of sulfur compounds cannot be wholly accounted for by their peroxide-decomposing action, and although they suppress peroxide-initiated autoxidation, they do not suppress oxidations initiated by free radical sources such as azobisisobutyronitrile (10). 

One generally applicable method of oxidation for alkyl bromides involves the Pummerer rearrangement. This gives aldehydes upon rearrangement of the alkyl aryl sulfoxide formed by displacement of halide by thiolate followed by oxidation (equation 41)358. 

The excellent resolution that can be achieved for closely related as well as structurally disparate polypeptides and proteins under a large variety of HPLC conditions, particular when gradient elution methods are employed. Two exemplars illustrate this point. With suitable optimization, polypeptide diastereoisomers can be easily resolved11 16 with RP-HPLC methods, while separation of deamidated or mono-methionine sulfoxide forms and subtle structural variants of recombinant globular proteins can be readily achieved23 24 30 139-142 with RP-HPLC, HP-HIC, HP-IMAC, or HP-IEX techniques. 

A tentative catalytic cycle (Scheme 7) has been proposed for the oxidation of sulfides with the new system. In this mechanism, the active species is the monomeric titanium complex 21, formed from the dimer titanium compound 20 by the action of 2-propanol. The alcohol also has a beneficial effect by displacing the sulfoxide formed, inducing the formation of 21, thereby permitting the catalytic cycle.54... 

The best results were obtained with (S)-(-)-phenylethyl hydroperoxide 47 at -20 °C in CC14, which afforded (S)-sulfoxides with low to modest enantioselectivity and low yield. A time profile of the oxidation of methyl p-tolyl sulfide with 47 showed that the asymmetric induction in the sulfoxidation was rather low (< 20%), demonstrating that the enantioselectivity obtained is related to a concomitant kinetic resolution of the sulfoxide formed. 

Reaction with organosulfur compounds. Perfluoroketene dithioacetals arise from perfluoroalkanedithiocarboxylic esters by attack of Grignard reagents on the doubly bonded sulfur atom, whereas 1-haloalkenyl aryl sulfoxides form a-haloalkenylmagnesium halides. ... 

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