Tertiary benzylic lithium compounds

A variety of tertiary benzylic lithium compounds have been prepared by addition of f-butyllithium in isooctane with TMEDA to substituted styrenes 34 at 243 K10 (equation 96). 

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. 

Whereas the lithium aluminium hydride reduction of an optically active benzylphos-phonium salt in tetrahydrofuran leads to a racemic or highly racemized tertiary phosphine and toluene, the reduction of (—)-benzyl(n-butyl)methylphenylarsonium bromide (68) or (S)-(-(-)-benzylmethylphenyl(n-propyl)arsonium bromide, (S)-(-I-)-64, with this reagent affords (—)-n-butyImethylphenylarsine, ( —)-12, or (S)-(-l-)-methyl-phenyl(n-propyl)arsine, (S)-(-)-)-65, of similar optical purity to the products obtained by cathodic reduction of the respective arsonium compounds (Table 4) . Moreover,... 

The or//io-palladation of 3,4-dioxygenated benzylic tertiary amines by lithium tetrachloropalladate can be directed exclusively to either C-2 or C-6. Substitution at C-6 prevails when AcO, methylenedioxy, PhCH20, methoxymethyl ether, or HO substituents are attached to C-3, whereas palladation occurs exclusively at C-2 when C-3 bears methylthiomethyl ether or phenylthiomethyl ether substituents. The resulting organopalladium compounds are crystalline solids, stable to air and moisture, and can readily be carbonylated, alkylated, arylated, Kinetic studies of the acetoxylation of arenes by potassium peroxydisulphate and acetic acid in the presence of (2,2 -bipyridyl)palladium(ii) acetate catalyst have led to a revision of the mechanism. The reaction is now thought to proceed via... 

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