Sulphoxides cyclic

Few 1 -benzothiophene-S-oxides 218 were obtained in moderate yields by treatment of 1-arylacetylenes 219 with sulfur dioxide and benzene in the presence of antimony pentafluoride250 (equation 127). A series of cyclic sulphoxides have been prepared by hydrolysis of the corresponding alkoxy sulphonium salts 220251-254 (equation 128). Syn-sulphoxide 221 was obtained in a low yield (15-20%) in the reaction of the dianion of cyclooctatetraene 222 with thionyl chloride255 (equation 129). 

Bis(4-hydroxyphenyl) sulphoxides butadienyl - see Butadienyl sulphoxides carbamoyl - see Carbamoyl sulphoxides chiral - see Chiral sulphoxides complexes of 567-573 conformational analysis of 84-89 cyclic - see Cyclic sulphoxides cyclopentanone - see Cyclopentanone sulphoxides... 

Sulphines may react as dienophiles with 1,3-dienes with the formation of cyclic sulphoxides. Unstable 2,2-dichloro-5,6-dihydro-2ff-thiin-l-oxide 191 was formed in an exothermic reaction between 173aandcyclopentadieneat — 40 (equation 101). The simplest, parent sulphine, CH2 = S = O, prepared in situ by treatment of a-trimethylsilylmethanesulphinyl chloride with cesium fluoride, reacts with cyclopentadiene to give bicyclic, unsaturated sulphoxide 192 as a mixture of two diastereoisomers in a 9 1 ratio (equation 102). On the other hand, a,j8-unsaturated sulphine 193 (generated by thermolysis of 2-benzylidene-l-thiotetralone dimer S-oxide) in boiling toluene behaves as a 1,3-diene and was trapped by norborene forming sulphoxide 194 in 78% yield ° (equation 103). 

The Horner-Wittig reaction of a-phosphoryl sulphoxides 442, which are chemically stable, results in the formation of a, -unsaturated sulphoxides 443 in high yields (equation 264). The reaction has been found to be non-stereoselective, mixtures of E and Z isomers being formed from aldehydes and unsymmetrical ketones . In the case of aromatic aldehydes this reaction can also be advantageously performed in a two-phase catalytic system even without the usual PTC catalysts (Table 24). Intramolecular Horner-Wittig reaction of a-phosphoryl-5-oxosulphoxides 444 leads to a, -unsaturated cyclic sulphoxides 445 (equation 265). Starting from optically active 0,0-... 

Electron-donating groups in the para position of the perbenzoic acid tend to decrease the rate of reaction . The reverse seems to be true when these groups are present in a 4,4 -disubstituted diaryl sulphoxide. The effect of ring size on the oxidation of cyclic sulphoxides is apparently very small in dioxane-water solution under either acidic or basic conditions . This suggests that no major hybridisation change occurs for the sulphur atom in going to the transition state. 

Like their 1-alkenyl analogues, 2-alkynylcysteine S -oxides and SS-dioxides in the presence of base undergo an internal addition of the amino-function to the triple bond to yield cyclic sulphoxides and sulphones. ... 

Thus 5-(2-propynyl)-L-cysteine 5 5 -dioxide ring-closes in dilute ammonium hydroxide solution to the ammonium salt of (72), which on the basis of n.m.r. data appears to exist in a half-chair conformation. Under more controlled conditions, (-f-)-5-(2-propynyl)-L-cysteine iS-oxide behaves similarly, giving the corresponding cyclic sulphoxide, but the cyclization of the (-)-isomer was unsuccessful. 

Stereochemical studies concerning oc-sulphinyl carbanions have clarified the conflict of interpretation of recent years of kinetic preference in exchange of diastereotopic protons a to the sulphinyl group. Studies of cyclic sulphoxides have shown that small changes in dihedral angle... 

Cl atom become trans— led to (44). Product analysis of a variety of other thian S-oxides fully supported the above mechanism. o-Bromination of six-membered-ring sulphoxides proceeded similarly. Highly stereoselective CK-chlorinations have also been reported for five-membered-ring sulphoxides the major products resulted from trans -additicm to the intermediate oxosulphenium ion. A survey and discussion of the methods available for the assignment of configurati( is of cyclic sulphoxides has been made. Benzene-, trifluoroacetic acid-, and [Eu(d m)3]-induced shifts were shown to be most reliable. A comparison of the size of of the... 

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