Lithium tetramethylpiperidide, structure

Studies of the positional Uthiation of pyridin-2-yl-substituted diazines are instructive each was subjected to excess lithium tetramethylpiperidide at -78 °C and then quenched with DCl the structures indicate the percentage of deuteration at each position. ... 

The products obtained from the reaction of (chloromethyl)trimethylsilane with organolithium reagents depend very much on the structure of the lithium compound. While lithium 2,2,6,6-tetramethylpiperidide initiates an a-elimination as described above, the treatment with sec-butyllithium leads to the formation of chloro(trimethylsilyl)methyllithium (11). This reagent cyclopropanates an electron-deficient alkene through sequential Michael addition and intramolecular ring closure (MIRC reaction), for example, the formation of cyclopropane 12. 

Robinson annulation although not extensively has been used in synthetic routes toward complex carbohydrate structures such as in the synthesis of 82. The starting ketone 80 reacts with (trimethylsilyl)but-3-en-2-one at -78 °C in the presence of lithium 2,2,6,6-tetramethylpiperidide (LTMP) base to give the alcohol 81. The a-methyl inverts to the axial position. The alcohol then produces the Robinson annulation adduct 82 in the presence of catalytic amount of methanolic potassium hydroxide in 58% yield. 

Treatment of either 144 or 145 with LDA gave, after quenching the reaction, the l, 2 -ene 146. If MeOD was used to quench the reaction, deuterium was incorporated at C-6 of the uracil ring. When anhydronucleoside 145 was treated with lithium 2,2,6,6,-tetramethylpiperidide, followed by quenching with TMSCl, the bis-TMS compound 147 was framed the mechanism of this process is unclear, but the structure of 147 was established by X-ray crystallography of a derivative. 

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