Diamines dilithiated

Dilithiated diamine 2 was synthesized by Karsch by a two-fold metalation of N,N,N, N tetramethylmethylenediamine (TMMDA) (1). The reaction was effected in n-pentane at low temperatures, yielding the poorly soluble Af,Af -bis(fithiomethyl)-Af,Af -dimethyl-methylenediamine (2) (Scheme 1). Due to its low solubility in toluene or THE, the highly pyrophoric compound was characterized by derivatization with several electrophiles, mainly chlorosilanes. Obviously, the addition of coordinating additives, such as TMEDA, DME (dimethoxyethane) or THE, does not enhance the solubility of the dilithium compound. Interestingly, as the author comments, TMEDA is only monolithiated in modest yields by alkyllithium bases. 

Numerous HCLA have been developed and used for the enantioselective isomerization of oxiranes to allylic alcohols and, in most cases, their efficiency strongly depends on the structure of the oxirane. The HCLA species can be divided into two groups monohthiated vicinal diamines or ether-amines and dilithiated diamines or amido-alcoholates. 

The bis(amido) monocyclic zirconium metallocene (11) was obtained by the reaction of equimolar amounts of the zirconocene dichloride Cp2ZrCl2 and the dilithiated diamine (Me3SiN-(CH2)2-NSiMe3)Li2 in THF (Scheme 5). (The latter... 

Although there are no informations available concerning the structure of the dilithiated 1,3-diamines in solid phase or in solution, subsequent reactions of la,b with di- and trichlorosilanes support the existence of these dianions. la,b are important building blocks in organoelement synthesis, not only restricted to the field of silicon chemistry. Remarkable results have been achieved in reactions with N- or C-substituted dichlorophosphanes. An extension to germanium and tin is possible, but side reactions or lower yields are often observed. Nevertheless, the facile double metalation of TMMDA and CMMDA is unique for tertiary amines (e g., the phosphorus homologue (CH3)2PCH2P(CH3)2 is only metalated at the methylene carbon atom [8]). 

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