Desulfurization with

The high nucleophilicity of sulfur atoms is preserved, even if it is bound to electron withdrawing carbonyl groups. Thiocarboxylales, for example, substitute bromine, e.g. of a-bromo ketones. In the presence of bases the or-acylthio ketones deprotonate and rearrange to episulfides. After desulfurization with triphenylphosphine, 1,3-diketones are formed in good yield. Thiolactams react in the same way, and A. Eschenmoser (1970) has used this sequence in his vitamin B]2 synthesis (p. 261). 

Gassman and co-workers developed a synthetic route from anilines to indoles and oxindoles which involves [2.3]-sigmatropic rearrangement of anilinosul-fonium ylides. These can be prepared from Ai-chloroanilines and ot-thiomcthyl-ketones or from an aniline and a chlorosulfonium salt[l]. The latter sequence is preferable for anilines with ER substituents. Rearrangement and cyclizalion occurs on treatment of the anilinosulfonium salts with EtjN. The initial cyclization product is a 3-(methylthio)indole and these can be desulfurized with Raney nickel. Use of 2-(methylthio)acetaldehyde generates 2,3-unsubstituled indoles after desulfurization[2]. Treatment of 3-methylthioindoles with tri-fiuoroacetic acid/thiosalieylie acid is a possible alternative to Raney nickel for desulfurization[3]. 

The Gassman synthesis has been a particularly useful method for the synthesis of oxindolcs[lb,8]. Use of methylthioacetate esters in the reactions leads to 3-(methylthio)oxindoles which can be desulfurized with Raney nickel. Desulfurization can also be done by reduction with zinc or tin[10,ll]. 

When desulfurized with Pb02, l-aryI 3-(4-p-tolyl-2-thiazolyl)thioureas yield the heterocyclic guanidines (262) (Scheme 159) (299, 496, 497). 

The thiones are readily desulfurized with Raney nickel to give the corresponding unsubstituted compounds in bicyclic systems in the 2-, 4- and 7-positions, and in tricyclic systems such as (95). The 2-methylthio derivatives may be similarly desulfurized. Thione groups in the 4-position, but not the 2-position, in pyrido-[2,3- f ]- and -[3,2- f]-pyrimidines may be replaced directly with ammonia or amines. 

Thiol groups in the 2-, 3- and 6-positions have been desulfurized with Raney nickel under the usual conditions to give the corresponding unsubstituted compounds. 

Desulfurization with Dry Lime Limestone or lime or dolomite (CaCO,3-MgCO,3) in a fluidized bed coal combustor reacts with SO9 in... 

Two serious drawbacks of this method are the extensive deuterium scrambling around the reaction site and the occasional formation of olefinic side products, which are hard to separate by conventional means. The extent of olefin formation may depend on the nature of the Raney nickel since it is known that desulfurization with deactivated Raney nickel can yield olefins. Best results are obtained when the deuterated Raney nickel is prepared very rapidly and used immediately after preparation. 

An older method,which also retains the double bond in its original location, utilizes the fact that thioketal formation from A" -3-ketones does not induce bond migration. Subsequent desulfurization with Raney nickel gives the A" -olefin (see section XI-D). 

In the course of synthesis of B-homo-progesterone (66) Himizu and Schichita utilized the Ringold procedure to convert 3j5,20 -dihydroxy-5a-pregnan-7-one diacetate (63) to 3/3,20yS-dihydroxy-B-homo-5a-pregnan-7-one diacetate (64). The latter is desulfurized with Raney nickel after prior... 

The aldol adducts 17 can be transformed by desulfurization with sodium amalgam to the substituted dihydroisoxazoles 20, or directly to /f/T-dihydroxy ketones by hydrogenolysis24. In general, chromatographic separation of the sulfmyldihydroisoxazoles 17 and/or their desulfurization products is possible and allows isolation of the enantio- and diastereomerically pure compounds24. 

Sulfinyl oxiranes 2 can be desulfurized with butyllithium at very low temperature to give oxiranes with retention of configuration as a result of a ligand exchange at sulfur (see also Table 6). However, with a benzylic substituent R1, an excess of butyllithium may at higher temperatures induce an elimination to an allylic alcohol. 

The diastereomeric lactones could be separated by chromatography and converted into optically active lactones by desulfurization with sodium amalgam or by pyrolysis to the corresponding butenolides. 

Since these adducts undergo reductive desulfuration with Raney nickel, optically active aryl methyl sulfoxides are versatile reagents for the conversion of imines to optically active amines. 

The addition of the lithium enolates of various acetic add esters to (S)-3-(4-methylphcnyl-sulfmyl)-2(5//)-liiranone and (,S)-5,6-dihydro-3-(4-methylphenylsulfinyl)-2//-pyran-2-one gives, after desulfurization with Raney nickel, 4-substituted dihydro-2(3//)-furanoncs and 4-substituted tetrahydro-2//-pyran-2-ones, respectively, in good to quantitative enantiomeric excess. Addition of the enolate occurs via the nonchelate mode. The enolate of methyl (phenylthio)acetatc is best overall in regards to chemical yields and enantiomeric purity of the final lactone product13. 

Docosanedioic acid has been prepared by Wolff-Kishner reduction of 6,17-diketodocosanedioic acid, formed by reaction of the half-ester acid chloride of adipic acid with the a,co-cadmium derivative of decane (%26 overall yield).3 Reduction of Wolff-Kishner method, followed by simultaneous reduction and desulfurization with Raney nickel of the 2,5-bis(co-carboxyoctyl)thiophene pro-... 

In addition, it has been reported that the rhenium polysulfido complex [Re(Cp )(S3)(S4)] (Cp =77 -C5Me5) undergoes desulfurization with Ph3P to... 

Newer secondary recovery plants use lead paste desulfurization to reduce sulfur dioxide emissions and waste sludge generation during smelting. Battery paste containing lead sulfate and lead oxide is desulfurized with soda ash to produce market-grade sodium sulfate solution. The desulfurized paste is processed in a reverberatory furnace. The lead carbonate product may then be treated in a short rotary furnace. The battery grids and posts are processed separately in a rotary smelter. 

Chrzanowska and Rozwadowska (60) performed a total synthesis of ( )-43, using amine 49 and the thioacetal of methoxycarbonylpiperonal (26) as substrates (Scheme 13). These two synthons were joined together under the influence of LDA, and the resulting addition product 50 was subjected to reductive desulfurization with Raney nickel to give racemic peshawarine (43). 

Sulfides are hydrogenolyzed usually by Ra-Ni.383-391 Phenyl and methylthio groups were removed by Ra-Ni (10 mmol Ni/mmol) refluxing in ethanol for 2 hours.392 A thio enol ether was desulfurized with Ra-Ni (100 mmol Ni/mmol) in MeOH at room temperature for 30 minutes.393 During the synthesis of 2-deoxy-p-gl y cos ides the removal of the arylthio group was achieved using Ra-Ni with no problem.394... 

A hydroxysulfoxide was desulfurized with Ra-Ni in MeOH for 30 minutes.400 Treatment with hydrogen in the presence of catalytic amounts of Ra-Ni in EtOH caused the desulfurization of a 2,6-anhydro-2-thio sugar, the reduction of an N-oxide, and the removal of benzyl and carbomethoxy groups at the... 

The keto function is frequently deoxygenated via Ra-Ni-mediated desulfurization of thioacetals 412 14 That is, the ketone group can be removed from compound (36) by thioketalization followed by desulfurization with Ra-Ni (81 mmol Ni/mmol) in MeOH for 20 minutes (Scheme 4.118).415... 

Samarium(II) iodide also allows the reductive coupling of sulfur-substituted aromatic lactams such as 7-166 with carbonyl compounds to afford a-hydroxyalkylated lactams 7-167 with a high anti-selectivity [74]. The substituted lactams can easily be prepared from imides 7-165. The reaction is initiated by a reductive desulfuration with samarium(ll) iodide to give a radical, which can be intercepted by the added aldehyde to give the desired products 7-167. Ketones can be used as the carbonyl moiety instead of aldehydes, with good - albeit slightly lower - yields. 

Kirimura, K. Furuya, T. Kino, K., et al., Method for Desulfurizing with Microorganism at High Temperatures. Patent No. JP2001231546. 2001, Aug. 28. 

Method for Desulfurizing with Microorganism at High Temperatures [114],... 

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