Lithium sulfide intermediate

The second step is also heterogeneous and involves the breakdown of the intermediate compound with further lithiation into lithium sulfide [12136-58-2] and finely divided iron [7439-89-6] particles. 

The 1-t-butylphospholane sulfide intermediate to TangPhos was also used to prepare the P,N ligands 48 by reacting the lithium complex with C02 and then oxazoline formation with a range of chiral amino alcohols [69b, 74]. The Ir complexes of these ligands have been successfully used in the reduction of / -methylcinnamic esters (80-99% ee) and methylstilbene derivatives (75-95% ee), a particularly challenging class of unfunctionalized olefins [4 c]. 

Vinyllithium [917-57-7] can be formed direcdy from vinyl chloride by means of a lithium [7439-93-2] dispersion containing 2 wt % sodium [7440-23-5] at 0—10°C. This compound is a reactive intermediate for the formation of vinyl alcohols from aldehydes, vinyl ketones from organic acids, vinyl sulfides from disulfides, and monosubstituted alkenes from organic halides. It can also be converted to vinylcopper [37616-22-1] or divinylcopper lithium [22903-99-7], which can then be used to introduce a vinyl group stereoselectively into a variety of a, P-unsaturated systems (26), or simply add a vinyl group to other a, P-unsaturated compounds to give y, 5-unsaturated compounds. Vinyllithium reagents can also be converted to secondary alcohols with trialkylb o r ane s. 

The beneficial effect of added phosphine on the chemo- and stereoselectivity of the Sn2 substitution of propargyl oxiranes is demonstrated in the reaction of substrate 27 with lithium dimethylcyanocuprate in diethyl ether (Scheme 2.9). In the absence of the phosphine ligand, reduction of the substrate prevailed and attempts to shift the product ratio in favor of 29 by addition of methyl iodide (which should alkylate the presumable intermediate 24 [8k]) had almost no effect. In contrast, the desired substitution product 29 was formed with good chemo- and anti-stereoselectivity when tri-n-butylphosphine was present in the reaction mixture [25, 31]. Interestingly, this effect is strongly solvent dependent, since a complex product mixture was formed when THF was used instead of diethyl ether. With sulfur-containing copper sources such as copper bromide-dimethyl sulfide complex or copper 2-thiophenecarboxylate, however, addition of the phosphine caused the opposite effect, i.e. exclusive formation of the reduced allene 28. Hence the course and outcome of the SN2 substitution show a rather complex dependence on the reaction partners and conditions, which needs to be further elucidated. 

Gasking and Whitham described the one-pot preparation of 1-silylated 3,3-di-methyl-substituted allenyl sulfides 307 (Scheme 8.82) [170]. Treatment of alkyne 305 with lithium thiolate generates allenyllithium species 306, which is subsequently silylated by trimethylsilyl chloride. Formation of lithiated intermediate 306 is based on a procedure developed by Clinet and Julia [171]. 

Tertiary and aromatic nitroso compounds are not readily accessible consequently not many reductions have been tried. Nitrosobenzene was converted to azobenzene by lithium aluminum hydride (yield 69%) [592], and o-nitrosobiphenyl to carbazole, probably via a hydroxylamino intermediate, by treatment with triphenylphosphine or triethyl phosphite (yields 69% and 76%, respectively) [298]. Nitrosothymol was transformed to amino-thymol with ammonium sulfide (yield 73-80%) [245], and a-nitroso-/J-naphthol to a-amino-/J-naphthol with sodium hydrosulfite (yield 66-74%) [255]. 

The classical preparation of alkyllithium compounds by reductive cleavage of alkyl phenyl sulfides with lithium naphthalene (stoichiometric version) was also carried out with the same electron carrier but under catalytic conditions (1-8%). When secondary alkyl phenyl sulfides 73 were allowed to react with lithium and a catalytic amount of naphthalene (8%) in THF at —40°C, secondary alkyllithium intermediates 74 were formed, which finally reacted successively with carbon dioxide and water, giving the expected carboxylic acids 75 (Scheme 30) °. 

Birch reduction, followed by acid treatment and addition of diazomethane leads to the A9(11)-enone 159 in 41% yield. Then, the double bond is hydrogenated and, by using PhSeCl and hydrogen hydroperoxide, the double bond A13 is formed. Treatment of the enone with lithium disopropylcuprate-dimethyl sulfide complex gives an intermediate enolate that is trapped again using PhSeCl. Enone 160 is obtained via oxidative elimination (62%). 

Thiiranes can be formed directly and stereospecifically from 1,2-disubstituted alkenes by addition of trimethylsilylsulfenyl bromide, formed at -78 C from reaction of bromine with bis(trimethylsilyl) sulfide (Scheme 7).12 A two-step synthesis of thiiranes can be achieved by addition of succinimide-A/-sulfe-nyl chloride or phthalimide-A -sulfenyl chloride to alkenes followed by lithium aluminum hydride cleavage of the adducts (Scheme 8).13 Thiaheterocycles can also be formed by intramolecular electrophilic addition of sulfenyl chlorides to alkenes, e.g. as seen in Schemes 914 and 10.13 Related examples involving sulfur dichloride are shown in Schemes 1116 and 12.17 In the former case addition of sulfur dichloride to 1,5-cyclooctadiene affords a bicyclic dichloro sulfide via regio- and stereo-specific intramolecular addition of an intermediate sulfenyl chloride. Removal of chlorine by lithium aluminum hydride reduction affords 9-thiabicyclo[3.3.1]nonane, which can be further transformed into bicyclo[3.3.0]oct-1,5-ene.16... 

The synthesis of 2C-T-17 R required starting with the S isomer of secondary butanol. The S 2-butanol in petroleum ether gave the lithium salt with butyllithium which was treated with tosyl chloride (freshly crystallized from naphtha, hexane washed, used in toluene solution) and the solvent was removed. The addition of 2,5-dimethoxythiophenol, anhydrous potassium carbonate, and DMF produced S 2,5-dimethoxyphenyl s-butyl sulfide. The conversion to R 2,5-dimethoxy-4-(s-butyl-thio)benzaldehyde (which melted at 78-79 °C compared to 86-87 °C for the racemic counterpart) and its conversion in turn to the nitro-styrene, S -2,5-dimethoxy-4-(s)-butylthio-B-nitrostyrene which melted at 70-71 °C compared to 68-69 °C for the racemic counterpart, followed the specific recipes above. The preparation of the intermediates to 2C-T-17 S follows the above precisely, but starting with R 2-butanol instead. And it is at these nitrostyrene stages that this project stands at the moment. 

By oxidising the sulfide to a sulfone, the synthetic versatility of this class of compounds is further increased. Deprotonation of either or both diastereoisomers of 98 leads, under thermodynamic control, to the equatorial organolithium 101 in which a destabilising interaction between the oxygen lone pair and the lithio substituent is avoided. However, lithium-naphthalene reduction of 102 to the organolithium 103 is axially selective because of the stabilisation afforded to the intermediate radical by the axial lone pair. Protonation of the product gives 104.88... 

Intermediates 663 can be prepared by tin-lithium transmetallation with w-BuLi from a-stannylated vinyl sulfides974. Starting from l,l-bis(arylsulfanyl)ethenes, a reductive metallation with lithium naphthalenide at —70°C is a very efficient approach to lithiated vinyl sulfides975,976. Other methods involved bromine-lithium exchange977 or addition of methyl or phenyllithium to thioketenes978. A convenient method for the preparation of l-(methylsulfanyl) and l-(phenylsulfanyl) vinyllithiums was the treatment of 2-methoxyethyl sulfides with 2 equiv of w-BuLi-TMEDA at — 30 °C979. 

Other lithiated vinyl sulfides bearing a carbonyl group at the / -position have been used in organic synthesis mainly as /3-acyl vinyl anion equivalents858. The 2-(isopropylsulfanylmethylene) derivative 673 has been deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LiTMP) to give the intermediate 674 which, after addition to methyl acrylate and final hydrolysis, afforded the cyclopentenone 675 in 70% overall yield981 (Scheme 175). 

Reduction of triazolinones with phosphorus sulfide has been one of the early routes to triazoles (05jcs625>. Milder reactions may differentiate between conjugation of the ring double bond with C=0 (139) or the lack of it (140) as in Scheme 48 (71bsf3296). The formation of triazole in the reduction of the triazolinone (140) with lithium aluminum hydride (vibsf3296) is explicable through the formation of a hydroxytriazoline intermediate. 

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