4- dibenzothiophene-, lithium

Reduction of dibenzothiophene with sodium in liquid ammonia has been shown to be sensitive to the experimental methods employed however, the major product is usually 1,4-dihydrodibenzothiophene. 27 -28i The electrochemical reduction of dibenzothiophene in ethylene-diamine-lithium chloride solution has been shown to proceed via stepwise reduction of the aromatic nucleus followed by sulfur elimination. In contrast to the reduction of dibenzothiophene with sodium in liquid ammonia, lithium in ethylenediamine, or calcium hexamine in ether, electrolytic reduction produced no detectable thiophenol intermediates. Reduction of dibenzothiophene with calcium hexamine furnished o-cyclohexylthiophenol as the major product (77%). Polaro-graphic reduction of dibenzothiophene 5,5-dioxide has shown a four-electron transfer to occur corresponding to reduction of the sulfone group and a further site. ... 

Cyclodehydration of 2-phenylthiocyclohexanone with a variety of reagents yielding 1,2,3,4-tetrahydrodibenzothiophene (64) as an oil has been reported,and represents the simplest way of obtaining this material (88%). Alternatively, reduction of 4-keto-1,2,3,4-tetrahydrodibenzothiophene under Huang-Minlon conditions affords 64 in high yield.Trace amounts of 64 were detected in the reduction of dibenzothiophene with calcium hexamine and during electrolysis in ethylenediamine-lithium chloride solution (Section III, C,4). Peracetic acid oxidizes 64 to its sulfone (65%), which... 

During the period covered by this review the preparation of most of the sets of four isomeric monosubstituted dibenzothiophenes have been completed. The successful synthesis of the 1-, 3-, or 4-substituted isomers is due largely to the synthesis of the four monolithiodibenzo-thiophenes by several groups of workers. Despite the success of this work which is due mainly to the established versatility of lithium reagents, the need exists for a separate study of the optimum conditions for the... 

N.B. Competition between the sulfonium formation and that of sulfoxide can be clearly exemplified with dibenzothiophene, where two different types of bases are used in situ (extraction of protons). With lutidine, sulfoxide is obtained probably from the residual water contained in the lithium perchlorate. On the contrary, insoluble bases (like inorganic carbonates) appear to strongly favor a mild electrophilic substitution. 

As an extension to this facile ligand exchange reaction, dibenzothiophene monoxide reacts with catalytic amounts of alkyl lithium reagent to afford oligomers of o-biphenylylene sulfide, via a dimer 19, as shown in Scheme 13 [45]. 

By this reaction, numerous organolithium compounds have been prepared from heterocycles. These heterocyclic lithium compounds can be those of pyridine, quinoline, carbazole, dibenzofuran, dibenzothiophene, etc. With some of these heterocyclic systems, there are made available organolithium compounds wherein the lithium is attached to carbon atoms otherwise inaccessible. We found them to be very helpful in our extensive heterocyclic investigations. 

Reaction at Sulphur.—The oxidation of benzo[6]thiophens to sulphoxides by t-butyl hypochlorite has been studied. In the presence of a ruthenium catalyst, dibenzothiophen was oxidized by oxygen to the sulphone. The reactions of benzo[ >]thiophen 1,1-dioxides with various reagents such as amines, amino-alcohols,3-aminopropylsilanes, and aromatic sulphonyl chlorides have been studied. Four detailed papers on the reaction of dibenzophenonium salts with aryl-lithiums have appeared in which the mechanism of ligand exchange was elucidated. " ... 

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