Lithiation transmetalation

For conversion of functionalized diorganozincs into tertiary amines, aromatic compounds which contain a directed metallation group, such as Af,Af-dialkylbenzamides, methoxymethyl phenyl ether, phenyl oxazolines and phenyl Af,Af-dialkylcarbamates, were ortho-lithiated, transmetallated and then aminated with 2a in good yields, but with a slower reaction rate (Scheme 19). 

It was also found that allenylzinc reagents, derived from TMS alkynes by the foregoing lithiation-transmetallation protocol, afford anti adducts in high yield upon treatment with aldehydes (equation 9). 

The furanylcerium that was generated from lithiation/transmetallation of furan 40 as shown in Equation (28) was a highly nucleophilic species that added readily to the sterically hindered ketopyrrole to provide the penultimate intermediate during the total synthesis of roseophilin <1998JA2817>. 

Symmetrical and unsymmetrical 2,5-fc/s-acetylenic furan derivatives were produced in high yield using Pd-catalyzed cross-coupling reaction of 2,5-/7M(butyltelluro)furan, which was prepared from furan through lithiation-transmetallation and alkylation <03TL1387>. 

Several 5-palladio triazoles have been prepared by a lithiation-transmetalation sequence. Interestingly, these pincer complexes can also be obtained by from kinetically controlled bidentate complexes 115 by a C5-H bond cleavage that gives the thermodynamically favored tridentate ones 117 (Scheme 35) [89]. 

The organometalhc precursors required for the introduction of COj are preparatively accessible through reaction of organic halides with metallic lithium or magnesium, metal-halogen exchange, ortho-lithiation, transmetallation or by deprotonation of CH-acidic sites, as described in the sections following. 

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