Lithium pyrrolidide

The existence of such complexes has been confirmed by kinetic experiments, multidimensional and multinuclear ( Li, H) NMR, and the beneficial effect of substitutions at the lithium pyrrolidide ring outlined . Nevertheless, recent computational studies... 

Die Anwendung einer nur katalytischen Menge eines Lithium-amids (Lithium-pyrrolidid) ist fur die mit 90%iger Ausbeute verlaufende Reaktion von Benzophenon-methylimin mit Isopren zu 2,2-Diphenyl-3-isopropenyl-pyrrolidin beschrieben3. 

In the presence of the corresponding pyrrolidine diamine, the chiral lithium pyrrolidide amide yields dimeric chelates composed of a lithium pyrrolidide amide dimer solvated by a pyrrolidine diamine, (Li-6)2 6, as shown by NMR spectroscopy39. The lithium amide gives two 6Li NMR signals in a 1 1 ratio. The addition of TMEDA to Li-6 results in a similar complex where TMEDA coordinates to the lithium pyrrolidide amide dimer, (Li-6)2 TMEDA. 

Unlike this reaction, the reaction of OFN with lithium dialkylamides easily proceeds at ambient temperature and results in the formation of hexa- 73-75 or heptaamines 76 and 77 in 41-46% yield63. The reaction occurs smoothly and selectively in dioxane or THF with two-fold excess of lithium dialkylamide per each fluorine atom. It is also recommended that UMPA be added to the reaction mixture (2 equivalents per 1 equivalent of the lithium amide), since cyclic ether solvents are prone to interact with non-solvated lithium amides and thus to form ring-opening products that then react with OFN. Lithium piperidide in either dioxane or THF gives exclusively the hexa-substituted derivative 75. Lithium dimethylamide produces hexaamine 73 in dioxane and heptaamine 76 in THF, whereas the most reactive lithium pyrrolidide forms in dioxane almost a 1 1 mixture of polyamines 74 and 77, and the only product in THF is 77. 

Dienes. Japanese chemists have prepared 1,5-dienes by reductive coupling of allylic haUdes with these complexes. For example, reaction of cyclohexylidenethyl bromide with the complex of lithium pyrrolidide and cuprous iodide in ether at 0° for 4 hr. gives the three products shown in equation I in essentially quantitative yield. The reaction is very sensitive, however, to the solvent and the temperature and also to the dialkylamine used for preparation of the catalyst. 

Related Reagents. Lithium Amide Lithium Hexamethyl-disilazide Lithium Diethylamide Lithium Piperidide Lithium Pyrrolidide Lithium 2,2,6,6-tetramethylpiperidide Potassium Diisopropylamide. 

Related Reagents. Lithium diethylamide lithium diisopro-pylamide lithium piperidide lithium pyrrolidide lithium 2,2,6,6-tetramethylpiperidide. 

In summary, chelating chiral lithium amides exist in either of four major structural motifs or mixtures of them (Scheme 3). Non-coordinating solvents generally favor cyclic trimers, A. Ladder tetramers are favored for pyrrolidide amides in the absence of coordinating solvents. 

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