Substituted sulfur derivatives

Oxygen can be introduced into the a-positions of thietanes by treatment of the thietane with lead tetraacetate as in the formation of (204) (75JOC3046). Thietanones can be prepared by hydrolysis of thiete enamines such as (205) (65LA(684)103) or by oxidation of 3-thietanol with DMSO/benzoic anhydride (78PS(4)167>. Thietanones can be converted into various ring-substituted sulfur derivatives as already illustrated in reactions of (68) and preparation of (199). 

In this context, it is worth mentioning that in natural meat volatiles mainly 2-substituted derivatives of furan or thiophene have been identified. This does not mean, however, that there are no 3-substituted sulfur-derivatives in natural meat products. It is more likely that these components substituted with sulfur in the 3-position are present in trace amounts in natural meat volatiles. 

Nucleophilic substitution on derivatives of sulfuric and phosphoric acids... 

NUCLEOPHILIC SUBSTITUTION ON DERIVATIVES OF SULFURIC AND PHOSPHORIC ACIDS... 

During the investigation of the synthesis and use of sulfilimines (such as 22 and 23) [21, 23, 24] and sulfondiimides (of the 25 type) [27], it became apparent that appropriately substituted nonsymmetric derivatives of these compounds were much more difficult to prepare in enantiopure form than their sulfoximine counterparts. It was therefore decided to retain the sulfur/oxygen moiety and to concentrate further efforts exclusively on the synthesis and application of sulfoximines. 

E. Analogues of Hydrocarbons Derived by Substituting Sulfur for a Tertiary Carbon Atom... 

The cyclization of certain 2-substituted isatin derivatives were studied so as to compare them with the above cyclizations. Thus, isatin- 2-thiosemicarbazone (126) and isatin-2-semicarbazone (127) underwent cyclization to 128 and 129 more easily than the corresponding cyclizations in the 3-series.406 As in the 3-series the sulfur compound underwent cyclization more easily than the oxygen.408 In contrast to... 

A number of thieno[3,2-6]thiophene derivatives have been synthesized by the acid-catalyzed cyclization of appropriately substituted acid derivatives. 3-Thienylthioacetic acid was cyclized with concentrated sulfuric acid to yield 14% of the ketone (158), which upon... 

The previously available methods for the preparation of such compounds were somewhat limited in their application. First, the oxidative coupling of 2 molecules of a heterocyclic-substituted toluene derivative in lie presence of sulfur results in the formation of symmetrical stil-benes,4,5 as shown by the synthesis of 4,4 -bis(benzimidazol-2-yl)stilbene (2). The disadvantages of this method are the high reaction temperatures necessary and the difficulties often involved in product workup. 

Non-anomeric positions can be regioselectively transformed by radical substitutions of halosugars or sulfur derivatives to yield mainly C-branched sugars by creation of new C-C bonds. 

Biodiesel is believed to be a promising alternative fuel to substitute petroleum-derived diesel fuel in diesel engines, and essentially no engine modifications are required to substitute biodiesel for diesel fuel. In addition, biodiesel is better than diesel fuel in terms of sulfur content, flash point, aromatic content, and biodegradability (1). Research on the commercial application of biodiesel has therefore been started in European countries, the United States, and Japan (2,3). 

An interesting photochemical synthesis of 2,5-disubstituted-thiophenes 38 stems from the first report of the photoinduced sulfur extrusion from variously 3,6-disub-stituted 1,2-dithiins 35a by exposure to daylight in ethyl acetate or in DCM, or by irradiation at 365 nm in methanol (Scheme 12.11) [29]. Other examples involve naturally occurring thiarubrines 35b [30], as well as variously substituted synthetic derivatives [ 31]. This photochemical reactivity has been generalized with an application in the synthesis of selenophene 40 obtained in almost quantitative yield from 39 [32]. 

The sulfur can be reductively removed by one of the many methods utilized for sulfur heterocycles. For the fused pyrimidine (703) zinc in acetic acid can be used (64JOC2135). In the 7-formylamino analogue (704), however, Raney nickel in aqueous ethanol was the best reagent for the reductive cyclization to form adenines (705) (78JOC960). It has been pointed out that nucleophilic substitution at C-7 in the [l,2,5]thiadiazolo[3,4-d]pyrimidine system easily takes place. This makes the compounds (704) readily available as key substances in this convenient approach to the synthesis of 9-substituted adenine derivatives. 

Nucleophilic substitution on chiral sulfur derivatives (the so-called Andersen method)... 

Carbolithiation reactions of ketone a,-dianions, generated by the above amine-free method with several alkenes, such as styrenyl derivatives, vinyl sulfides and vinylsilanes, can lead to the generation of ketone a,5-dianions (Scheme 15)14. For example, when one equivalents of triphenylvinylsilane was treated with a ketone a,-dianion, in THF, at 0 C for 1 h and the resulting reaction mixture was quenched by 2.2 mol equivalents of trimethylchlorosilane, the corresponding bis-silylated enol silyl ether was obtained. Substituted styrenyl derivatives, such as 1,1-diphenylethylene and cinnamyl alcohol, also underwent a smooth carbolithiation to give the corresponding ketone a,5-dianions. Similar addition reactions of ketone a,f)-dianions to vinyl phenyl sulfide took place smoothly to give a,5-dianions with a sulfur attached in the 5-position. 

Eight-membered heterocyclic rings with three heteroatoms rarely occur as structural blocks of natural products and their synthetic analogues. The first example of natural 1,2,3-trithiocanes has been reported recently <2002EJ02400>. Two novel sulfur derivatives 183 and 184, one of which is a glycoside, containing substituted 1,2,3-trithiocane cycles were isolated from Perophora viridis which was collected off the Atlantic coast of North Carolina. 

There is an extensive chemistry of substituted sulfur fluorides of the types RSF3 and RSF5 examples of the former were mentioned previously. The SF5 derivatives bear considerable resemblance to CF3 derivatives, with the principal difference that in reactions with organometallic compounds the SF5 group is fairly readily reduced, whereas the CF3 group is not. 

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