Lithium mercaptides

Reactions with organometalllc substrates. One useful reaction of this and other trialkylborohydrides is cleavage of metal carbonyl dimers to metal carbonyl anions (equation I). The by-products are Hj and B(C2Hs)3. Another useful reaction is the generation of anionic formyl complexes (equation II). Sulfur (Sg) can be cleaved to give either LijS or Li2S2 (equations III and IV). Disulfides are cleaved by this reaction to lithium mercaptides. 

Although a conventional initiation of anionic polymerization by alkyl lithiums involves their addition to a C=C bond, an exceptional mode of initiation associated with ring-opening polymerization was reported by Morton and Kammereck186). Ethyl lithium seems to initiate polymerization of propylene sulphide, but the reaction involves first a desulphuration of the monomer, leading to the formation of lithium mercaptide ... 

On the other hand, lithium mercaptides do not initiate polymerization of the analogous 4-member cyclic sulphides and their reaction with ethyl lithium proceeds in a conventional way ... 

The lithium mercaptide groups are then hydrolyzed with acids. 

A number of compounds of the types RSbY2 and R2SbY, where Y is an anionic group other than halogen, have been prepared by the reaction of dihalo- or halostibines with lithium, sodium, or ammonium alkoxides (118,119), amides (120), azides (121), carboxylates (122), dithiocarbamates (123), mercaptides (124,125), or phenoxides (118). Dihalo- and halostibines can also be converted to compounds in which an antimony is linked to a main group (126) or transition metal (127). 

The dependence of the counterion and of the solvent99 was studied in the addition of sec-butyl and tert-butyl mercaptide to methyl 4-bromocrotonate (3). The highest yield of the Michael addition induced cyclopropane product 10 was observed with lithium as counterion in dichloromethane or pentane as solvent. 

Finally the methyl ester is cleaved with lithium n-propyl-mercaptide by nucleophilic displacement and the benzyl ether by conventional catalytic hydrogenolysis to furnish (-)-scopadulcic acid (1). 

The unique feature of the alkyllithium compounds that makes them useful as diene initiators is their character as exceedingly powerful bases yet they are soluble in organic solvents and quite thermally stable. Alkyllithium compounds are sufficiently basic to add to hydrocarbon monomers. However, lithium salts of stabilized anions, such as acetylide and fluorenyl anions, are too weakly basic to add to such double bonds. Similarly, alkoxides and mercaptides fail to react with hydrocarbon monomers, but lithium alkyl amides react analogously to alkyllithium compounds. 

A partial synthesis of this metabolite has also been reported by Buehi and Wo-gan84, proceeding to the optically active natural product (18) by means of demethyla-tion (lithium alkyl mercaptides) of natural aflatoxin Bt (i) in good yield. 

This reaction had been effected previously with lithium iodide in refluxing 2,6-lutidine (1, 615-616). This combination afforded 25-28% of starting material, 49-51% of the desired acetoxy acid, and 5-10% of the hydroxy acid. Use of the mercaptide reagent converted the acetoxy ester into 3/3-acetoxy-A5-etiani c acid in 92% yield (25°, 24 hours). 

CLEAVAGE OF ETHERS Aluminum chloride. Boron tribromide. Bromine. Dimethylformamide. Methylmagnesium iodide. Triphenylphosphine dibromide. a-GLYCOLS Silver iododibenzoate KETOXIMES Chromous acetate METHYL ESTERS Lithium n-propyl mercaptide. 

In order to realize the synthesis of ( )-isozonarol (86), the ketone (82) was treated with excess methyllithium in ether. The resulting alcohol on dehydration with dimethyl sulfoxide followed by chromatographic purification over 15% silver nitrate on silica gel afforded ( ) isozonarol dimethyl ether (85). Its demethylation with lithium n-butyl mercaptide in hexamethylphosphoric triamide furnished ( )-isozonarol (86). 

Lithium(3,3-dimethyl-l-butynyl)-l,l-di-ethoxy-2-piopenyl cuprate, 300 Lithium dimethyl cuprate, 301-302 Lithium di-n-octylcuprate, 356 Lithium diphenylphosphide, 302 Lithium (fl-(E)-propenyl cuprate, 302-303 Lithium divinyl cuprate, 190 Lithium-Ethylamine, 284-286, 472 Lithium fluoride, 244 Lithium hexamethyidisilazide, 337 Lithium B-isopinocampheyl-9-borabi-cycloj 3.3.1) -nonyl hydride, 303 Lithium N-isopropylcyclohexylamide, 169 Lithium o-lithiobenzylate, 67 Lithium (l-lithiopropionate, 303 Lithium methyl mercaptide, 303-304 Lithium methylthioformaldinc, 305 Lithium naphthalenide, 303, 305-306 Lithium perchlorate, 212 Lithium n-propylmercaptide, 283 Lithium selenophenolate, 306-307 Lithium 2,2,6,6-tetramethylpiperidide, 299, 307-308... 

Lithium methyl mercaptide, CHsSLi. Mol. wt. 54.04, stable off-white solid. The material is prepared by the reaction of methyllithium with methyl mercaptan in anhydrous ether at 0°(N2). A slurry of CHuSLi is formed, from which ether and... 

Mercury.—The bridgehead mercurials (1) and (2), prepared, respectively, from the corresponding lithium (3) or magnesium (4) compound and a mercuric halide and from the lithium derivative (5) and mercuric chloride, have seen service in studies on polyfiuorobicyclo [2,2,1 ]heptyl derivatives of sulphur (see p. 290). Each mercurial undergoes fluoride-initiated (CsF in DMF at 80 C) reaction with sulphur to yidd the corresponding mercaptide (6), presumably via a transient intermediate with pronounc carbanionic character (c/. refs. 16, 17) or even a polyfluorobicyclo-... 

An improved reagent for the G-alkyl cleavage of methyl esters by nucleophilic displacement has been found by a Stanford group lithium n-propyl mercaptide (from n-butyl-lithium and n-propyl mercaptan) in hexa-methylphosphoramide smoothly and selectively cleaves methyl esters to the corresponding carboxylic acid salts. The use of boron trichloride in dichloro-methane is recommended for the cleavage of sterically hindered methyl esters methyl ethers are unaffected. 

A new one-pot synthesis of azo-compounds from hydrazodicarboxylic acid esters appears to be an improvement over existing methods for the same transformation. Cleavage of (54) with lithium methyl mercaptide and subsequent oxidation with aqueous potassium ferricyanide at 0 °C gives the azo-compound (55) in 82% yield (Scheme 34). 

Ethylene sulphate underwent ring opening with nucleophiles such as amines, mercaptides, acetylides, and alkyl-lithiums to give 3- ubstituted ethyl sulphates. ... 

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