Lithium-ate complex

Analogous lithium ate complexes 53 are detected by NMR when solutions of PhLi are treated with HMPA,65 and the formation of an intensely yellow solution in the halogen-metal exchange of the diiodide 54 with BuLi suggests the intermediacy of the ate complex 55.66... 

Non-Cp ligands [119-127] those containing heteroatom compounds have been extensively explored as spectator ligands by virtue of their strong metal-heteroatom bonds and exceptional and tunable steric and electronic features required for compensating coordinative unsaturation of metal centers and for catalytic activity toward polymerization. The elegant non-Cp-ligated cationic yttrium aluminate species applied in the polymerization of 1,3-dienes was reported by Okuda. Both the yttrium aluminates (31a) and their lithium ate complexes (31b) upon activation... 

The nucleophilic reactivities of organocopper-lithium ate complexes are lower than those of either a Grignard reagent or organolithium compounds. Then they are able to add to the 1,4-position of the double bond conjugated with ketone or the other carbonyl groups [79]. 

Asymmetry s. a. Chirality Ate complexes s. Cuprates, Lithium ate complexes C-Atoms, labeled s. Compds., labeled Anrones... 

In contrast to the intermediate hydroxystannanes, O-protected stannanes 7 are stable compounds which can be distilled or chromatographed and stored under nitrogen for months. Treatment of 7 with butyllithium in tetrahydrofuran at — 78,JC results in rapid tin/lithium exchange (< 1 min). No products resulting from Wittig rearrangement or formation of an ate complex 8 could be detected9. 

These reagents are not isolated but are used directly in reactions with aldehydes, after generation of ate complexes via the addition of an alkyllithium reagent or pyridine11. 2-(2-Propenyl)-1,3,2-dioxaborolane is also metalated upon treatment with lithium tetramethylpiperidide, but mixtures of a- and y-substitution products are obtained upon treatment of this anion with alkylating agents20. Consequently, this route to a-substituted allylboron compounds appears to be rather limited in scope. 

We came up with the idea of using a dummy ligand, as shown in Scheme 1.23 [34]. Reaction of dimethylzinc with our chiral modifier (amino-alcohol) 46 provided the methylzinc complex 62, which was subsequently reacted with 1 equiv of MeOH, to form chiral zinc alkoxide 63, generating a total of 2 moles of methane. Addition of lithium acetylide to 63 would generate an ate complex 64. The ate complex 64 should exist in equilibrium with the monomeric zincate 65 and the dimer 66. However, we expected that the monomer ate complex 64 and the mono-... 

The TMEDA and THE complexes of the very sterically crowded methyllithium derivative tris(trimethylsilyl)methyUithium (9, Scheme 1) were studied by multinuclear solid state NMR spectroscopy in combination with solution NMR spectroscopy and X-ray crystallography to reveal the strucmre and dynamic behaviour of the complexes . In the solid state, this complex crystallizes as an ate-complex, with one lithium cation interacting with two substituted methyl anions while the other lithium cation is complexed by two TMEDA ligands. In solution, the afe-complex is partly transformed into solvated monomers or aggregates, depending on the experimental conditions. 

The reaction of the lithiated species with deuterium oxide proceeds with retention of configuration due to the coordination of the electrophile to the lithium cation. However, the corresponding ate complex is formed with inversion because no coordination of the Lewis acid is possible at the lithium cation and, therefore, the protonolysis of the ate complex proceeds with inversion of configuration. Among the Lewis acids examined, triethylaluminum gives the best result. 

Sato and coworkers fonnd that site-selective iodine-magnesinm exchange reactions of 1,4-diiodo-l,3-alkadienes were attained only by nsing the organomagnesinm ate complex, lithium dibutylisopropyhnagnesate (Scheme 9). The magnesiated iodoalkadienes were transformed into polysnbstitnted styrenes and phenols. 

Another highly useful heterobimetallic catalyst is the aluminum-lithium-BINOL complex (ALB) prepared from LiAlH4 and 2 equiv. of (/ )-BINOL. The ALB catalyst (10 mol %) is also effective in the Michael reaction of enones with various malonates, giving Michael products generally with excellent enantioselectivity (91-99% ee) and in excellent yields [23]. These results ate summarized in Table 8D.3. Although LLB and LSB complement each other in their ability to catalyze asymmetric nitroaldol and Michael reactions, respectively, the Al-M-(/ )-BINOL complexes (M = Li, Na, K, and Ba) are commonly useful for the catalytic asymmetric Michael reaction. 

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