Vinyllithium derivative

Starting with l,l-bis(trimethylsilyl)ethylene (5) in hexane or diethyl ether as the solvent we obtained another dimeric product, a monolithiumorganic compound 8 which was shown not to be formed by lithium hydride elimination from the 1,4-dilithiobutane derivative 6, the only product in THF as the solvent. Obviously the vinyllithium derivative 7, primarily formed in the same manner as vinyllithium from ethylene [4], in contrast to vinyllithium [4] does not add further lithium atoms but adds itself to the starting material 5 yielding 8 ... 

In the preparation and use of a series of 5 variously substituted 1-aryl-l-vinyllithium derivatives (Ar = phenyl, dimethylphenyl or isopropylphenyl Ri = H, Me or 4-tolyl R2 = D, Me or 4-tolyl), all operations had to be under purified nitrogen to prevent explosion. 

ALKYLMETAL HALIDES, ALKYLMETALS ARYLMETALS, 1 - ARYL-1 -VINYLLITHIUM DERIVATIVES GRIGNARD REAGENTS, HALO-ARYLMETALS ORGANOLITHIUM REAGENTS... 

The Shapiro reaction provides a convenient, easy and straightforward method to convert ketones into a plethora of olefinic substances in high yields. Many of these vinyllithium derivatives are useful for further synthetic manipulations. No attempt is made in this chapter to cover all the applications of the Shapiro reaction and only few representative examples will be described. A variety of polyolefins such as 119, used for cation olefin cyclization, can be stereospecifically formed in a concise and modular approach in a single step from the components shown in equation 42 via the Shapiro reaction . 

The nitrile 153 similarly can be formed below - 105°C by a kinetically controlled deprotonation with LDA, but on warming above -100°C it readily rearranges to the thermodynamically more stable vinyllithium derivative 154 [77AG(E)853]. In contrast the morpholino derivative 155 is... 

These experiments demonstrate that vinyllithium derivatives react with electrophiles with retention of configuration. 

The first method involves generation of an unstable vinyllithium derivative at low temperatures from the corresponding vinyl halide or 1-hydroalkene Addition of zinc chloride and warming to room temperature gives the stable vinyl zinc reagent [100, 101, 102,103] (equations 69-72)... 

Aryl-l-vinyllithium derivatives, 46 Assessment of reactive chemical hazards, 46 Atomic absorption spectroscopy (aas), 48 Autoignition incidents, 49 Autoignition temperature, 49 Autoxidation, 51... 

Imines of acylsilanes are excellent precursors of SMA (See Section III.B.l.m). Insertion of an isonitrile into the C-Li bond of a lithium reagent, followed by the silylation of the resulting vinyllithium derivative affords such imines.160... 

In an unconventional cyclopentenone synthesis, Negishi cyclised vinyllithiums derived from the 1-iodo- 1-silyl alkenes 103 onto preformed lithium carboxylate salts.57 He later found58 that amides 104 function in this reaction rather better than the carboxylate salts, and that the silyl substituent is not necessary for cyclisation. Nitriles, on the other hand, fail to cyclise. 

Five-menibered ring synthesis via cyclization of vinyllithium derivatives... 

Trigonally hybridized vinyllithium derivatives are characterized by higher configurational stability [34,35]. Panek [36] demonstrated that (E) and (Z)-l-lithium-l-phenyl-l-butene could be prepared stereospecifically, with retention of configuration, by a lithium-halogen exchange reaction between n-butyllithium and (Z) and ( )-l-bromo-l-phenyl-1-butene, respectively (Scheme 7). Both lithium derivatives are configurationally stable at... 

Scheme 6. Formation of o-lithiostyryllithium 27 starting from the vinyllithium derivative ( )-14, R = Ph.

P. Quayle and co-workers utilized the Dotz benzannulation reaction for the synthesis of diterpenoid quinones." The authors developed a novel synthetic approach to 12-O-methyl royleanone using a simple vinyl chromium carbene complex along with a disubstituted oxygenated acetylene. The bicyclic hydrazone was converted to the corresponding vinyllithium derivative by the Shapiro reaction and then functionalized to give the desired crude Fischer chromium carbene complex. The benzannulation took place in refluxing THF with excellent regioselectivity, and the natural product was obtained in 37% overall yield from the hydrazone. 

The products of the amino-Claisen rearrangement can in turn be involved in further isomerizations such as an aromatic di-rr-methane (ADPM) rearrangement98. Another noteworthy rearrangement is that occurring by treatment of V-allylaniline 58 with tert-butyllithium to give V-(2-methylene-4-pentenyl)aniline 60 via a vinyllithium derivative 59 (so-called 6-endo intramolecular carbometallation)99 (equation 24). 

This Sn-Li exchange is widely used for the construction of very comphcated structures. A vinyllithium derived from vinylstannane by Sn-Li exchange has been used for synthesis of a polycyclic ether (Scheme 12.43) [112]. This synthetic process relies on the tendency of triflates to undergo Sn2 substitution with the cy-cloalkoxyvinyllithium generated in situ. 

The tin-lithium exchange methodology for access to vinyllithium derivatives has been used for syntliesis of C s-symmetric hydropyran cyclooligolides (Scheme 12.44) [113]. In this process, an aldehyde derived from readily available ethyl (S)-lactate was treated with cuprate which had been prepared by addition of organolithium and Cul to vinylstannanes, and various types of building block were successfully constructed. 

Trapping reactions of vinyllithium derivatives generated from tosylhydrazones with DMF in TMEDA produce a,/ -unsaturated aldehydes in 10-65% yields as illustrated in equations 66 and 6754,58. 

In l-hthio vinyl sulfides (sec. 8.6) the sulfur atom stabilized the carbanion, allowing either alkylation or condensation reactions. The sulfonyl moiety can also stabilize a vinyllithium derivative. Vinyl sulfone (321), for example, was converted to the 1-lithio derivative with methyllithium.332 xhis organometallic reacted in the usual manner with alkyl halides (methyl iodide) to give the coupling product, 322. 

A variety of organolithiums, including benzylic, vinylic, alkynic, and 1-alkoxylithium compounds, are also accessible through the lithium-tellurium exchange, which involves the treatment of diorganotellurides with w-BuLi at —78 °C in THF (eq 25) 222 vinyllithium derivatives have been prepared from the corresponding organomercurials by essentially the same... 

Knorr R, von Roman TF (1984) Configurational stability of vinyllithium derivatives with 1-trimethylsilyl and 1-alkoxy substituents. Angew Chem Int Ed 23 366-368... 

Vinyllithium derivatives 128-131 have been generated through a bromine-lithium exchange with t-BuLi. In the case of 128, used in the synthesis of (-)-wode-shiol, a deprotonation of the alcohol functionality was performed prior lithiation [107]. Intermediates 129 were also used in the synthesis of triquinanes [102,108], meanwhile 130 acted as an intermediate in a synthetic route to (-i)-pericosine B [109]. Dianionic species 131 showed an unexpected intramolecular carbometalla-tion upon addition of TMEDA to give dilithiated dihydropyrroles, which finally reacted with different electrophiles [110]. 

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