Sulfides cyclic

The reaction of butadiene with sulfur gives the disulfide 112, cyclic sulfide 113, and macrocyclic mono- and trisulfides 114 and 1I5[105]. 

The proton affinities (gas phase) of thiirane and other three-membered heterocycles have been determined azirane (902.5), thiirane (819.2), phosphirane (815.0), oxirane (793.3 kJ moF ) (80JA5151). Increasing s character in the lone electron pairs decreases proton affinities. Data derived from NMR chemical shifts in chloroform indicate the order of decreasing basicity is azirane > oxirane > thiirane (73CR(B)(276)335). The base strengths of four-, five- and six-membered cyclic sulfides are greater than that of thiirane. 

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). 

An interesting addition reaction of sulfur dichloride has been discovered that allows the preparation in good yield of bridged cyclic sulfides from cyclic dienes. Two examples of the reaction have been described (cyclo-octadiene and in the other 1,5-cyclooctadiene. The former sequence is shown in the scheme. The experimental details of the latter sequence are given below. 

Monobasic carboxylic acids with an a-methyl group Esters of aliphatic dibasic carboxylic acids Cyclic sulfides... 

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

Reaction of dihalides with sulfide ion (cyclic sulfides)... 

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

The initial step of the adsorption of cyclic sulfides on a Mo(100) surface is also the formation of adsorbed thiolate groups.395-397 Adsorbed alkyl thiolates decompose to adsorbed sulfur, carbon, and hydrogen on the clean Mo surface, but once the surface is deactivated by adsorbed sulfur, alkanes and alkenes evolve from the surface. Tetrahydrothiophene (34) and trimethylene sulfide decompose on Mo(110) to alkanes and alkenes by way of a common intermediate, which is proposed to be a surface thiolate (33). The thiolate undergoes hydrogenation or dehydrogenation, depending on the surface hydrogen concentration (Scheme 4.115).398 399... 

A well-known characteristic of medium-sized rings (8- to 11-membered) is their ability to undergo facile transannular reactions. Cere et al. found that acid-catalyzed transannular cyclizations of 8-10-membered 7,5-unsaturated cyclic sulfides yield fused bicyclic sulfonium salts independently of the geometry of the double bond <1998J(P2)977>. 

The same group reported the trimethylsilyl iodide-promoted transannular cyclization of the eight-memebered cyclic sulfide, rra r-4,5-dihydroxythiocane 46 <1997JOC8572>. As expected this intramolecular Sn2 reaction gave only one product, o-4-hydroxy- r-thioniabicyclo[3.3.0]octane iodide 47, as shown in Equation (15). 

Transannular cyclizations of nine-membered cyclic sulfides provided a novel route to thioanalogues of swainsonine derivatives. Treatment of the enantiopure polyhydroxylated thiacyclononane derivative 48a with trimethylsilyl iodide yielded the bicyclic sulfonium salt 49a as a single diastereomer, as shown in Equation (16) <2003JOC3311 >. The presence of a C2-axis and the complete regio- and stereoselectivity of the transannular substitution led to a single configurationally homogeneous product irrespective of the fact that the sulfur atom would attack C-5 or C-6. 

As described earlier (Sect. 6.2.4.6), the solid reagent system, IBD-alumina, is a useful oxidizing agent and its use is extendible to rapid, high yield and selective oxidation of alkyl, aryl and cyclic sulfides to the corresponding sulfoxides upon microwave activation (Scheme 6.35) [110]. 

At the beginning of the last century, Bruning and Autenrieth24 suggested for the first time that the reaction of cyclic sulfide 1 with bromine results in formation of a disulfonium dication 2. It was shown later that the actual reaction product is dibromodisulfide 3 (Scheme 2).25... 

The photolysis of carboxylic acids and derivatives as lactones, esters and anhydrides can yield decarboxylated products 253>. This reaction has been utilized in the synthesis of a-lactones from cyclic diacyl peroxides 254) (2.34) and in the synthesis of [2,2]paracyclophane by bis-decarboxylation of a lactone precursor (2.35) 255). This latter product was also obtained by photoinduced desulfurization of the analogous cyclic sulfide in the presence of triethyl phosphite 256). 

The reaction described is of considerable general utility for the preparation of benzoyloxy derivatives of unsaturated hydrocarbons.2"8 Reactions of 2-butyl perbenzoate with various other classes of compounds in the presence of catalytic amounts of copper ions produce benzoyloxy derivatives. Thus this reaction can also be used to effect one-step oxidation of saturated hydrocarbons,9, 10 esters,6,11 dialkyl and aryl alkyl ethers,12 14 benzylic ethers,11,15 cyclic ethers,13,16 straight-chain and benzylic sulfides,12, 17-19 cyclic sulfides,11,19 amides,11 and certain organo-silicon compounds.20... 

Upon irradiation in benzene, cyclic thiolsulfonate [64] undergoes the interesting photochemical transformation shown in (183), affording the highly strained cyclic sulfide [69] in 97% yield (Meinwald et al., 1976). This sulfide can be oxidized with m-chloroperbenzoic acid to the corresponding strained sulfoxide... 

A hypervalent iodine(III) reagent, Ph—1=0, together with TMS-azide, promotes direct a-azidation of cyclic sulfides the reaction opens up a route to unstable N,S-acetals. ... 

The acid-catalysed transannular cyclization of 8-10-membered y,5-unsaturated cyclic sulfides (59) or (60) yields c/x-fused bicyclic sulfonium salts (61) independently of the geometry of the double bond. The rate varies linearly with the acidity function -(Ho h with a slope of 1. The rate variations span a range of about 10 , the maximum rate difference being observed for the ( /Z)-thiacyclooct-4-ene pair. The data are consistent with the classical interpretation of the intramolecular reactivity in terms of internal strain of the substrate and/or of the transition state. ... 

Cyclic sulfides treated with triethyl phosphite eject sulfur and form a new ring less one member [577], From compounds containing sulfur in three-membered rings (thiiranes) alkenes are formed in high yields [291, 294. The same reaction can be achieved with triphenyl phosphine [291]. 

The 3- and 4-membered cyclic sulfides, referred to as thiiranes (also episulfides) and thie-tanes, respectively, are easily polymerized by both cationic and anionic initiators, such as... 

Although there are no reported polymerizations of simple cyclic sulfides of ring size 5 and higher, polymerizations of 1,3,5-trithane (the cyclic trimer of thioformaldehyde) (LX), disulfides such as l-oxa-4,5-dithiacycloheptane (LXI), and trisulfides such as norhonene trisulfide (LXII) have heen achieved [Andrzejewski et al., 1988 Baran et al., 1984 Moore et al., 1977 Zuk and Jeczalik, 1979]. 

Vulcanization by heating with sulfur alone is a very inefficient process with approximately 40-50 sulfur atoms incorporated into the polymer per crosslink. Sulfur is wasted by the formation of long polysulfide crosslinks (i.e., high values of m in XHI), vicinal crosslinks (XIV), and intramolecular cyclic sulfide structures (XV). (Structures XIV and XV do not contribute significantly to the physical properties of the polymer.)... 

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