Crystalline organolithium complexes

X-ray structures for various crystalline organolithium complexes are covered in Chapter 3 which provides proof for chelate ring structures as opposed to open chain polymeric structures. It also supports the NMR finding of increased ionic character in the Li-C bond upon solvation of the lithium (10). 

Recently, Hoppe has shown that asymmetric deprotonation of propargyl carbamates 218 can lead to enantiomerically enriched alkynes 220 [126]. Treatment of 218 with -BuLi in the presence of (-)-sparteine 85 gives a crystalline organolithium complex 219 which reacts with electrophiles to yield enantiomerically enriched alkynes 220. Invertive transmetallation with ClTi(0-f-Pr)3 generates... 

With the exception of methyllithium, all types of organolithium compounds have yielded 1 1 complexes with bidentate, tridentate, or tetradentate chelating tertiary poly amines (16). Most are crystalline but BuLi TMED is an oil. 

Work with TED (triethylenedimaine) showed that reasonable metalation rates were obtained only at ratios of 1 1 in benzene. The reaction required 2.5 hours in refluxing benzene for completion. The bright yellow, crystalline product had a modest solubility in benzene and precipitated from solution. The solid complex may be pyrophoric in large amounts. The solubilities of various organolithium-tertiary diamine complexes are listed in Table II. 

Synthetic Application of (Benzyllithium —TMED A and Benzyl-lithium—TED. All the synthetic application studies were run with an aged (benzyllithium)2-TMEDA toluene solution that had 0.8% of the total organolithium compounds present as the tolyllithium isomers (only meta present) or with benzyllithium-TED crystalline complex free of ring isomers. 

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