Sulfoxide bonded complexes

Bajoras and Makuska investigated the effect of hydrogen bonding complexes on the reactivities of (meth)acrylic and isotonic acids in a binary mixture of dimethyl sulfoxide and water using IR spectroscopy (Bajoras and Makuska, 1986). They demonstrated that by altering the solvent composition it was possible to carry out copolymerization in the azeotropic which resulted in the production of homogeneous copolymers of definite compositions at high conversions. Furthermore, it was shown that water solvent fraction determines the rate of copolymerization and the reactivity ratios of the comonomers. This in turn determines the copolymer composition. 

An oxygen-bonded sulfoxide complex will be termed anO-RjSO complex, and similarly, a sulfur-bonded complex will be termed an S-RjSO complex. Where the mode of coordination is not known or is uncertain, formulas of the type [M(R2SO)xC1 ] will be used. 

In non-HBD solvents such as n-heptane, tetrachloromethane, diethyl ether, deuterio-tri-chloromethane, and dimethyl sulfoxide, tropolone transfers its proton to triethylamine to give an ion pair, which is in equilibrium with the non-associated reactants. There is no formation of a hydrogen-bonded complex between tropolone and triethylamine because of the fact that tropolone itself is intramolecularly hydrogen-bonded. The extent of the ion pair formation increases with solvent polarity. In polar HBD solvents such as ethanol, methanol, and water, this proton-transfer equilibrium is shifted completely towards the formation of triethylammonium tropolonate [171]. 

The absorption bands in the infrared spectra of monobromo-substituted anilines in both the free molecules and the hydrogen bonded complexes with dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and hexamethapol (HMPA) are studied134. The temperature... 

Sulfoxides form hydrogen-bonded complexes with a-methoxyphenylacetic acid, which results in differential shielding of the two substituents. ... 

Cryoscopy and NMR spectroscopy have been used to probe the structures of sulfur-stabilised allyllithium species in solution. In THE endo-monomers predominate, but it is also suggested that the structures are dependent on the oxidation state of sulfur. Hence, 1-thiophenylallyllithiumexhibits an equilibrium between two q -bonded complexes with the Ca-Li contact ion pair (CIP) being preferred, whereas the sulfoxide analogue reveals both static, THF-bonded q Ca-Li and q Cy-Li CIPs and for the lithiosulfone several solvated conformations are in rapid equilibrium. ... 

Methyl m-tolyl (8), ethyl m-tolyl, methyl n-butyl and methyl n-propyl sulfoxides were obtained in 100% e.e. This method was less successful when applied to methyl phenyl sulfoxide (5% e.e.) or to methyl isobutyl and methyl ethyl sulfoxides (25% e.e.). No complexes were formed between methyl o-tolyl, methyl p-tolyl, methyl 2-butyl and methyl isopropyl sulfoxides so these compounds could not be resolved using 7. A crystal structure of the 1 1 complex formed between 7 and 8 revealed that the partners were linked by OH—OS hydrogen bonds in endless zig-zag chains23. More recently, 2-chloroethyl m-tolyl sulfoxide (9) has been resolved using 724. 

An optically active sulfoxide may often be transformed into another optically active sulfoxide without racemization. This is often accomplished by formation of a new bond to the a-carbon atom, e.g. to the methyl carbon of methyl p-tolyl sulfoxide. To accomplish this, an a-metallated carbanion is first formed at low temperature after which this species may be treated with a large variety of electrophiles to give a structurally modified sulfoxide. Alternatively, nucleophilic reagents may be added to a homochiral vinylic sulfoxide. Structurally more complex compounds formed in these ways may be further modified in subsequent steps. Such transformations are the basis of many asymmetric syntheses and are discussed in the chapter by Posner and in earlier reviews7-11. 

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