Lithium organo- compounds alkylation

Thus, even 2,6-dibromo-l,4-quinone adds lithium organo compounds to give 4-alkyl-4-hydroxy-2,6-dibromo-2,6-cyclohexadien-l-ones125>. When bulky t-butyl groups are in the ortho positions of one of the carbonyl groups, such as in... 

The mechanism for coupling with these organometallic compounds could be illustrated as follows. First an organo-lithium (RLi) compound is prepared from the alkyl halide. In this case the alkyl halide is isopentylbromide. 

Unlike elimination and nucleophilic substitution reactions, fonnation of organo-lithium compounds does not require that the halogen be bonded to 5/) -hybiidized car bon. Compounds such as vinyl halides and aryl halides, in which the halogen is bonded to sp -hybiidized carbon, react in the sane way as alkyl halides, but at somewhat slower rates. 

The rearrangement of an ether 1 when treated with a strong base, e.g. an organo-lithium compound RLi, to give an alcohol 3 via the intermediate a-metallated ether 2, is called the Wittig rearrangement. The product obtained is a secondary or tertiary alcohol. R R can be alkyl, aryl and vinyl. Especially suitable substrates are ethers where the intermediate carbanion can be stabilized by one of the substituents R R e.g. benzyl or allyl ethers. 

Some new initiators soluble in hydrocarbons were described during the last few years. Organo-lithium compounds form 1 1 complexes with alkyls of Mg 134,135), Zn 136) or Cd l36), and their usefulness as initiators of anionic polymerization of styrene and the dienes was established 137). 

Organocadmium compounds can be prepared from Grignard reagents or organo-lithium compounds by reaction with Cd(II) salts.180 They can also be prepared directly from alkyl, benzyl, and aryl halides by reaction with highly reactive cadmium metal generated by reduction of Cd(II) salts.181... 

It was already established that pure ethyl-" " and f-butyllithium exist as six- and fourfold polymers, respectively, in benzene solution. Apparently, C—Li bond cleavage takes place in this solvent leading to an exchange of alkyl groups between polymeric organo-lithium molecules when both compounds are present. The products are believed to be electron-deficient polymers of the type (EtLi) (f-BuLi) , wha-e m is a small number such as 4 or 6. ... 

The most stable structures of alkyl and alkenyl anions predicted with the VSEPR theory are supported by reliable calculations. There are no known experimental structural data. In fact, up to recently, one would have cited the many known geometries of the lithium derivatives of these carbanions as evidence for the structure. One would simply have dropped the C—Li bond(s) from these geometries. However, it is now known that the considerable covalent character of most C—Li bonds makes organo-lithium compounds unsuitable models for carbanions. 

Organo magnesium halides and organo lithium compounds are readily accessible alkylation and arylation reagents. However, they have little practical importance for the preparation of diorgano tellurium derivatives. Tellurium tetrachloride cannot be alkylated or arylated stepwise to give, for instance, diorgano tellurium dihalides, which could... 

The related f-butyl derivative 347 was metallated with w-BuLi and the resulting organo-lithium compound 348 was alkylated with alkyl and allyl iodides, bromides and chlorides in the presence of HMPA519. From 349, several different types of deprotection reactions were possible. Direct hydrolysis to the corresponding aldehydes has been performed under... 

Lithium alkanetellurolates, prepared from tellurium and an alkyl lithium compound or dialkyl ditellurium derivatives and hthium, and sodium arenetellurolates, obtained from diaryl ditellurium compounds and sodium borohydride ", reacted with triorganosilyl, -germyl, -stannyl, and -plumbyl chlorides to produce, for instance, organo triorganosilyl tellurium compounds. 

Alkyl organo tellurium compounds, prepared from alkane- or arenetellurolates and alkyl halides, react with butyl lithium,. 9ec-butyl lithium, /ert.-butyl lithium, or phenyl lithium. The alkyl group bonded to the tellurium atom is cleaved from the tellurium and is present in solution as the alkyl lithium that can be used for further reactions. This tellurium-lithium exchange reaction is synthetically useful, whenever the alkyl halides cannot be converted to alkyl lithiums by other, more conventional halogen exchange reactions. The following exchange reactions were successfully carried out ... 

Various alkyl and aryl substituted pentaorganoarsenic compounds are known - . Most of these have been synthesized by transmetallation from Grignard reagents or organo-lithium reagents to arsenic centers. 

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