Sulfides cyclic, oxidation

RCH=CHZ —> RCHJCHODialkylchloroboranes, obtained as the major products of hydroboration of 1-alkenes with monochloroborane complexed with dimethyl sulfide, are oxidized by PCC to aldehydes (66-68% yield). Similar oxidation of dialkylchloroboranes derived from cyclic alkenes with PCC gives ketones in 70-85% yield. 

When a prochiral sulfide is submitted to the oxidation by DMD or TFD, the corresponding racemic sulfoxide is produced, whereas in the case of a chiral sulfide, diastereoselective oxidation is feasible. For example, a good diastereoselectivity was obtained with the chiral cyclic disulfide in equation 21. ... 

The typical S-oxidation with BVMOs allows the formation of chiral sulfoxides from organic sulfides. This oxidation has received much interest in organic chemistry due to its use in the synthesis of enantiomerically enriched materials as chiral auxiliaries or directly as biologically active ingredients. This reaction has been studied extensively with CHMO from Adnetohacter showing high enantioselectivi-ties in the sulfoxidation of alkyl aryl sulfides, disulfides, dialkyl sulfides, and cychc and acyclic 1,3-dithioacetals [90]. CHMO also catalyzes the enantioselective oxida-hon of organic cyclic sulfites to sulfates [91]. 

Dialkyl sulfides, alkyl aryl sulfides, diaryl sulfides, and cyclic sulfides are oxidized to the corresponding sulfoxides or sulfones. Often, both products can be obtained on oxidation with the same oxidant, depending on... 

A large number of alkyl aryl sulfides were oxidized electrochemically under superdry conditions using MeCN as solvent and BU4NBF4 or LiC104 as supporting electrolytes for cyclic voltammetry and preparative electrolyses, respectively [97]. 

Metallocomplex asymmetric oxidation of sulfides including oxidation of cyclic sulfides and derivatives of heterocycles with sulfide groups as substituents 03ZOR1607. 

Thiolation of secondary alcohols is not the preferred route to synthesize secondary mercaptans, because of the facile dehydration that occurs under reaction conditions of the secondary alcohols. H2S can also react with aliphatic or cyclic oxides, viz., ethers to produce the corresponding thioethers or sulfides. This is one of the preferred ways to make tetrahydrothiophene or thiophene. 

Miscellaneous Systems Many systems have been mentioned [li,m,2i] acyloxy and acylsilyl phosphine oxides, phosphine sulfides, cyclic compounds, benzoyloxa-ziridine derivatives, dibenzoylmethane derivatives, triazene and pentaazadiene moiety containing compounds. New developments include benzyl benzoin benzyl ethers [112], dithiocarbamates [113], ketoamides [114], phosphonates [115], bromo-acetylpyrene [116], alkylimides [117], aryloxy naphthalene [118], oligosilanes [119], bisphosphine sulfides [120], sulfamic esters of benzoin ethers [121], sulfur [122], or carbohydrate [123] containing compounds. 

Sulfides are oxidized to sulfoxides. C Tioval of a benzylthioethyl group from makes the group base-labile. When the si ears chiral ligands, the oxidation becom< Cyclic thioamides are desulfurized to i C=N — C=0. Ketoximes, hydra onyl products. 

Several substances in this group contain a sulfide group, which would be metabolized by S-oxidation. These include simple sulfides and sulfoxides for which S-oxidation would be the main route of metabolism (Nos 452 60, 507, 533,1683, 1684,1685 and 1707), acyclic sulfides with oxidized side-chains, which would have alternative processes of elimination (Nos 461-463, 465-481,495-503, 505,1297, 1298,1668,1677,1688-1692,1703 and 1710), and cyclic sulfides, some of which have additional functional groups, providing alternative processes of elimination (Nos 456, 464, 498, 499, 534, 543, 550, 563, 1296 and 1685). The majority of the combined intake of all compounds was from methyl sulfide (No. 452). The Committee concluded that under the current conditions of use as flavouring agents, the combined intake of these substances would not saturate S-oxidation and combined intakes would not raise safety concerns. 

Copper-based scavengers (formation of insoluble copper sulfide) Iron-oxide-based scavengers (formation of insoluble iron sulfide) Formaldehyde/methanol (formation of water-insoluble, cyclic thio compounds) Glyoxal (formation of thio acetals and other compounds)... 

Many monomers respond to a specific class of initiator or initiating mechanism with the exclusion of all others. Isobutylene polymerizes only cationically, not anionically or free radically. It is highly probable, therefore, that an initiator that induces polymerization in isobutylene acts cationically. Acrylates and methyl methacrylate do not polymerize cationically, but free radically or anionically. Cyclic sulfides and oxides do not undergo a free radical polymerization. Alternatively, monomers can also be used to test an initiator, if different initiators lead to completely different polymer structures. 2-Vinyloxyethyl methacrylate is polymerized cationically be means of the vinyl group, anionically via the acrylic group, and free radically via both groups (cross-linked polymers). Another possibility consists of the copolymerization of two different monomers (see Chapter 22). Suitable pairs are shown in Table 15-4. 

In contrast to simple sulfides, cyclic dithioacetals have four sulfur lone pairs in one molecule that can participate in oxidation processes, but the presence of a substituent at the 2-position raises the issue of diastereoselectivity as well as enantioselectivity. Potentially, four stereoisomers of the monoxide... 

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. 

The conversion of cyclic sulfides to sulfones is accompbshed by more energetic oxidations. Perhalogenated thiolanes [106] and 1,3-dithietanes [107] are oxidized to sulfones and disulfones, respectively, by a mixture of chromium trioxide and nitric acid (equation 98) The same reagent converts 2,4-dichloro-2,4-bis(tnfluoromethyl)-l,3-dif/u cto cs to disulfone derivatives [107], whereas trifluoromethaneperoxysulfonic acid converts the starting compound to a sul-fone-sulfoxide derivative [2(equation 99). 

Succinates (e.g., dicyclohexyl succinate) Hexafluoropropylene oxide (HFPO) dimers and trimers Fluorochloro compounds having CFC12 Malonic acids C(0)CH2C(0)0CH3 Cyclic sulfides... 

A useful comparison of the 13C shifts for acyclic and cyclic five- and six-membered sulfur compounds has been made86,220, but data on cyclic sulfur compounds of other ring sizes are rather limited. Typically, oxidation of sulfide to a sulfone results in 20-25 ppm... 

The common route for the synthesis of medium-size ring sulfoxides and sulfones is oxidation of the corresponding cyclic sulfides70, which are obtained from the interaction of a, w-dihaloalkanes with sulfide ion in fair to good yields243 (equation 110). 

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