Phenylthiomethyllithium

We owe to Corey and Seebach [302] an efficient procedure for the generation of phenylthiomethyllithium (PhSCH2Li), opening the way for practical applications. They found that this reagent was produced in about a 97% yield through reaction of equimolar amounts of n-butyllithium, DABCO and thioanisole in THF at 0°C for 45 min. 

Phenyl 4-pentenedithioate 42 2-(Phenylthio)cyclooctanone 55 Phenylthiomethyllithium 86 Pummer reaction 64,81... 

The two schemes showing homologation of halides through alkylation of phenylthiomethyllithium as the key step for carbon-carbon bond formation illustrate the potential of this reagent [303],... 

Phenylthiomethyllithium. C6H5SCH2Li is prepared by reaction of n-BuLi with thioanisole in THF containing DABCO.1... 

BUTENOLIDES D i methylformamide dimethyl acetal. Dimethylsulfonium methylide. Peracetic acid. Phenylthiomethyllithium. Titanium(IV) chloride. Trifluoroacetyl chloride. 

Diastereoselective addition of Phenylthiomethyllithium and subsequent treatment affords optically active lactones with >90% ee (eq 7). ... 

Phenylthiomethyllithium (2a) was used for the homologation of primary halides in a two-step sequence first halogen displacement by reagent (2a) or the organocuprate derivative (in the case of allylic compound) and then replacement of the phenylthio group by iodo by heating the sulfide with a large excess of methyl iodide in 1 M sodium iodide solution in DMF (Scheme 16). 

Phenylthiomethyllithium was also used for ketone methylenation, - mainly in the case of hindered ketones which do not react with the usual Wittig reagent. This is a three-step sequence the reagent (2a) is added, then the resulting alcohol is acylated, and finally the exocyclic methylene is formed by reduction with lithium in ammonia (Scheme 17). 

The heteroalkenes were prepared by Peterson-type alkenation of the corresponding aldehydes with bis(trimethylsilyl)phenylthiomethyllithium [PhS(Me3Si)2CLi] followed by oxidation to sulfones. 

Lithio-l,3-oxathiane - has proved to be much less reactive than phenylthiomethyllithium (Scheme 74, entry a).- Although the latter reacts well with alkyl or benzyl bromides and with alkyl iodides without distinction, 2-lithio-l,3-oxathiane works well only with alkyl iodides. ... 

As an intramolecular process for converting the very reactive acyllithium, we examined the possibility of / -elimination from an acyllithium having a suitable leaving group to afford a ketene as an intermediate [Scheme 5-2 (c)]. To test this possibility, phenylthiomethyllithium, whieh is easily available via the deprotonation... 

Phenylthiomethyllithium, C6H5SCH2Li [1, 849, before 4-Phenyl-l,2,4-triazoline-3,5-dione]. Mol. wt. 130.13. 

In the case of allylic halides somewhat higher yields are obtained if the complex of phenylthiomethyllithium and cuprous iodide is employed. This complex is prepared by stirring phenylthiomethyllithium with a slight excess of cuprous iodide in THF at — 50° to form a fine grey suspension of phenylthiomethylcopper. With this reagent allyl bromide is converted into 4-iodo-l-butene in 52% yield. 

Phenyl-l,2,3,4-tetrachloro-7,7-dimethoxy-norbornadiene, 401 5-Phenyltetrazole, 404 Phenylthiomethylcopper, 324 Phenylthiomethyllithium, 99, 324 l-Phenyl-l,2,3-tnazole, 45... 

Metatation Corey and Seebach2 treated thioanisolc and n-butyl bromide and the reagent in THF at 0° and obtained phenylthiomethyllithium in 97% yield. 

Homologation Acrolein. Carbon monoxide. Cuprous bromide-Diazomethane. Ethyl bromo acetate. Ethyl diazoacetate. Methyl vinyl ketone. Phenylthiomethyllithium. Trimethyl phosphite. 

As an example, the methyl group in thioanisole can be metalated using n-butyllithium to produce phenylthiomethyllithium by contrast, anisole under the same conditions is metalated at an ortho position. This reaction has been of little practical use in synthesis since the maximum yield of the lithium intermediate is only about 35%. However, Corey and Seebach (23) recently developed an excellent procedure for generating phenylthiomethyllithium in essentially quantitative yield by reaction between equimolar amounts of thioanisole, n-butyllithium, and DABCO in tetrahydrofuran at 0°C. 

Almost optically pure 3-substituted y-butyrolactones were obtained by the following sequence i) the reaction of 6-alkylideneoxazepine 9 with phenylthiomethyllithium in the presence of a catalytic amount of nickel chloride, ii) the transformation of the adduct to the dihydrofuran derivatives 11 by trimethyloxonium tetrafluoroborate, iii) acid hydrolysis of the dihydrofuran derivative 11. ... 

Oxidation of allylic and homoaUyic alcohols. A convenient route to 3-thioalkyl-2-cycloalkenones is based on the established pattern of transpositional oxidation of tertiary allylic alcohols. The substrates are readily prepared by reaction of the enones with phenylthiomethyllithium or l,3-dithian-2-yllithium reagents. 

Phenylthio)ethanols, 596 Phenylthiomethyllithium, 463, 596 2-Phenylthiopropionic acid, 466 Phenylthiotrimethylsilane, 399 cis-l-Phenyl-2-(p-tolylsulfonyl)ethene, 486... 

A larger C-ll-C-25 fragment of (-f )-milbemycin P is prepared by a somewhat similar strategy (Scheme 98) [154]. Addition of phenylthiomethyllithium to 590 gives a 1 3 mixture of diastereomers 678 and 679 that is difficult to separate. Furthermore, the desired diastereomer 678 represents the minor component of the mixture. Consequently, the mixture is transformed to epoxide 680, which is then allowed to react with aluminate 681 to provide a more easily separable mixture of alcohols. After separation, the major (undesired) alcohol is converted to the desired 682 by Mitsunobu inversion with 4-nitrobenzoic acid. 

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