Lithium complexes groups

The concept of using group I metal initiators was applied in order to minimize the toxicity generated by heavy metal residues in the end product PLAs when using metals like aluminum, tin, and lanthanides as initiators. In recent years, dinuclear lithium and macro-aggregates with phenolate ligands have attracted substantial interest, mainly due to uncommon strucmral feamres and their ability to catalyze formation of polyester and various other polymeric materials via ROP [28]. A series of lithium complexes supported with 2, 2-ethylidene-bis (4, 6-di-tert-butylphenol) (EDBP-H2) 2-6, (Scheme 6) are excellent initiators for the ROP of L-lactide in CH2CI2 at 0 °C and 25 °C [33-35]. In this case, the PDIs of the obtained PLAs were quite narrow (1.04—1.14) and a Unear relationship between and the monomer-to-initiator ratio ([M]o/[I]o) existed at 0 °C. Dimeric complexes 4 and 6 were the... 

The crystal structure of the lithium complex [Pr 2N(Ph)COLi(p-tmp)(p-Bu )ZnBu shows that the amide solvates the lithium ion through oxygen with zincation of the aryl occurring via interaction of the ortho aryl hydrogen Bu or tmp group." The crystal... 

Bayle presented liquid crystal 34 (Scheme 19) bearing four aromatic units linked by ester and azo functional groups [56]. Two butyloxy groups are attached at the ends of the molecule and the crown ether is bound at the side of the molecule. The nematic phase exhibited by 34 is quite broad (AT = 96 K). Upon complexation with LiBF4, the nematic range diminishes with increasing amounts of added salt and disappears completely at 0.5 equiv. of added LiBF4 which is most likely due to the formation of a 2 1 crown lithium complex. From 0.2 equiv. of salt, a smectic... 

The lithiation of anisylpyridines has been studied.80 Whereas usual reagents did not react or gave addition products on the pyridine ring, the BuLi-LiDMAE superbase has induced exclusive pyridino-directed metallation. The latter selectivity has been attributed to an internal cooperating lithium complexation by both the pyridine nitrogen and methoxy group. 

Secondary amines can be acylated with acyl groups bearing no a-hydrogens. Deprotonation next to the nitrogen atom and introduction of electrophiles allow the oxidation of that position. Eaiiy work showed that these anions underwent self-condensation. For example, A(,lV-dimethylbenzainide can be deproton-ated with lithium 2,2,6,6-tetramethylpiperidide (LITMP) to give Af-methyl-lV-phenacylbenzamide in 60% yield. It is clear that lithium ion is crucial to the success of this reaction. Ctown ethers prevent the reaction,and recent kinetic studies show intermediate lithium complex formation. ... 

The majority of reports dealing with Group IA complexes of 2,2 -bipyridine are concerned with the species (M(bpy) . The lithium complexes Li2(bpy) and Li(bpy) have been used (primarily by Herzog and... 

If the tetrahydroisoquinoline moiety is connected to a chiral bidentatc complexing group, e.g., 4, then the preformed complex with butyllithium results in rapid removal of the proton from the st-face, forming the lithium complex. In contrast to alkylation, deuteration of this complex by dimethyl sulfoxide-fif6 occurs with retention of configuration (5)11. 

The crystal structures of the lithium salts 8 with bulky aryl substituents exhibit monomeric structures and / -coordination of the dithiocarboxylate to the lithium atom (Fig. 2) [40]. Lithium complexes 9 and 10,bearing pyrazyl and pyridyl groups, respectively, also have monomeric structures, the former of which has / -coordination similar to that of 8. On the other hand, the lithium cation in 10 is chelated by one sulfur atom of the dithiocarboxylate and a nitrogen atom of the pyridyl group [4]. 

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