From vinyllithium reagents

Vinylcopper reagents and vinylcuprates can be prepared from vinyllithium reagents in the same manner as for alkyl and aryl reagents. In addition, vinylcopper... 

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. 

A variation of this strategy involves conjugate addition of the reagent formed from a 1 1 mixture of dimethylzinc and a vinyllithium reagent. The presence of dimethylzinc suppresses... 

Chamberlin and coworkers38 showed that vinyllithium reagents derived from ketone (2,4,6-triiso-propylphenyl)sulfonylhydrazones undergo intramolecular carbolithiadon reactions with high dia-stereoselectivity (Scheme 13). 

The first vinyllithium carbolithiation reaction was reported by Chamberlin and Bloom15, who showed that vinyllithium reagents derived from ketone trisylhydrazones undergo anionic cyclization reactions to give functionalized cyclopentanes (Scheme 4). These authors have also shown that 5-, 4- and 3-alkyl-substituted 2-lithio-l,6-heptadienes like... 

Neuman, H. Seebach, D. Chem. Ber., 1978, III, 2785, report a detailed study of generation of vinyllithium reagents from vinyl bromides, and reactions thereof. 

Allylboronates homoallylic alcohols. Vinyllithium reagents react regio- and ster-eospecifically with this a-chloroboronic ester (1) to form an ate complex (a) that rearranges to an allylboronate (2) Allylboronates are known from the work of Schlosser and Hoff-... 

This coupling is equally applicable to alkyl-, aryl-, and vinyllithium reagents. The products are obtained in generally good yield and in 98-100% isomeric purity. The reaction can also be used to prepare vinyl sulfides from vinyl halides and a lithium thiolate (equation II). 

The crucial role of chelation in terms of increasing rigidity and reactivity of chiral dienophiles was first demonstrated (1983) with a-hydroxy ketone derivatives (Scheme 83, Table 18). Conjugated a-hy-droxy ketones (340) and their enantiomers were prepared via separation of acid (338) from its enantiomer, followed by successive treatment with Bu"Li and the appropriate vinyllithium reagent (339). 

Scheme 7-70 Intramolecular carbocyclization from a vinyllithium reagent.

A further method for substitution is provided by the vinyllithium reagent available in two steps from 2,3-dibromopropene1 s. Addition to aliphatic aldehydes allows isolation of the TMM precursor in good yield. 

Compound (E) was prepared from levoglucosan and, after transformation into its tosylate and the corresponding epoxide, was opened with DMSO anion to give a dimethylated alcohol after desulfurization. The alcohol was then transformed into the corresponding lactol. Reduction of the lactol to the expected triol followed by a tandem protection-oxidation process afforded an aldehyde, which was then coupled with the vinyllithium reagent generated from the corresponding vinyl iodide [190]. The major diastereoisomer was transformed, after a... 

Most Shapiro reactions of acyclic sulfonylhydrazones or cyclic sulfonylhydra-zones derived from larger rings proceed with selectivity for the formation of the E-vinyllithium reagent. For example, the trisylhydrazone generated from 4-heptanone (12)... 

This reaction can be extended to di- and trisubstituted alkenes by use of substituted vinyllithium reagents. These can be prepared quantitatively from vinyl chlorides or bromides by reaction in ether with lithium powder (containing 2% sodium) or from vinyl bromides by halogen—metal exchange with an alkyl-lithium. 

In both cases, sulfur stabilized the lithium derivative and reaction with alkyl halides proceeded in a manner analogous to other vinyllithium reagents. Hydrolysis required mercuric salts or another Lewis acid to give the ketone, as in the preparation of Ph2CHCOMe from 367. Another preparation involves direct treatment of an... 

Addition of vinyllithium reagent 636 to 632 occurs largely from the re side (Felkin—Anh selectivity) to give the anti diastereomer 637 (85% de) [193]. Lithium—bromine exchange at — 78 °C followed by protonation affords 638 in 89% yield with complete retention of olefin geometry. Ozonolysis of 638 followed by lithium aluminum hydride reduction of the intermediate aldehyde furnishes protected triol 639 in 78% yield. 

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