1.2- Dicarbanionic compounds

Reduction of a conjugated enone to a saturated ketone requires the addition of two electrons and two protons. As in the case of the Birch reduction of aromatic compounds, the exact order of these additions has been the subject of study and speculation. Barton proposed that two electrons add initially giving a dicarbanion of the structure (49) which then is protonated rapidly at the / -position by ammonia, forming the enolate salt (50) of the saturated ketone. Stork later suggested that the radical-anion (51), a one electron... 

Benzyl-type carbanions and their metallo compounds, derived from aromatic or hetero-aromatic precursors, bearing carbon- or hetero-substituents, are readily available with variable substitution patterns due to their mesomeric stabilization (see Section 1.3.2.2)2. Even dicarbanions are accessible without difficulty3,4. The equilibrium acidities of many aromatic hydrocarbons have been determined5-7. The acidities of a-hetero-substituted toluenes8 are similar to those of the corresponding allylic compounds and can usually be generated by the same methods. 

Compounds of the type CH3CO—CH2—CO— can give up two protons, if treated with 2 moles of a strong enough base, to give dicarbanions ... 

End-to-end cydization methods can be divided into bimolecular and uni-molecular processes. One consists of bimolecular cydization between a living a. j-dicarbanionic polymer and a difunctional electrophile compound under extreme dilution conditions. 

Treatment of acetylmethylenetriphenylphosphorane with /i-butyllithium or lithium diisopropylamide results in abstraction of a methyl proton to form an yiide anion. Reactions of the 1,3-dicarbanion with electrophilic compounds including alkyl halides, aldehydes, ketones and benzoate esters occurs at the terminal carbanion site to afford a variety of substituted -ketophosphonium ylides (equation... 

In a detailed study of the generation of dicarbanions from /3-dicarbonyl compounds, Harris and Harris found that sodium amide is superior to potassium amide, sodium methylsulfinylmethylide, or sodium hydride. 

Dimerization of fi-dicarbonyl compounds. The dicarbanions of 3-dicarbonyl / compounds are dimerized by treatment with iodine (or bromine) when catalyzed by cuprous chloride or cobaltous chloride. ... 

Analogously, the reaction of the inert diradical PTBT with Bu4N HO in THF gives an excellent yield of the expected dicarbanion PTBT , isolable as the Bu4N salt (p. 375). The latter can also be obtained from the corresponding a/7,a//-quasiperchloro compound with Bu4N" HO" in THF (189). 

We have synthesized some novel silarylene and silarylenesiloxane polymers via dicarbanions prepared from Lochmann s base. Lochmann s base, a powerful metalating reagent composed of equimolar amounts of n-butyl lithium and potassium r-butoxide in a hydrocarbon, has been used to dimetalate compounds such as m-xylene, 4,4 -dimethylbi-phenyl, and 2,3-dimethyl-1,3-butadiene in good yields. In this work the dicarbanion of m-xylene and 4,4 -dimethylbiphenyl have been used to prepare silicon containing monomers and polymers by two different routes. The first route involves a 1 1 condensation reaction between the dicarbanion and a dichlorodiorganosilane to produce a condensation polymer. The second route involves reaction of the dicarbanion with a chlorodiorganosilane which is then converted to a bis(silanol) and then polymerized. Spectroscopic as well as thermal characterization will be presented on the polymers which have been described. 

Free-radical reactions have found many synthetic applications and can sometimes successfully replace older type reactions, such as the Wurtz synthesis. Diisopropyl peroxydicarbonate is an effective initiator particularly suited for low temperature reactions. Another recent development is the increased use of dicarbanions and other dianions as intermediates for the prepn. of compounds which are otherwise difficult to obtain... 

Sulphonyl carbanions usually effect a simple addition to carbonyl compounds to afford carbinols, as exemplified by the reaction of (98) with benzaldehyde. " The aa -dicarbanions of dimethyl sulphone and dibenzyl sulphone reacted with two moles of benzophenone in a similar manner. 

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