The first high yield preparation of non n-stabilized bis(lithiomethy1)silanes was performed by the reductive cleavage of C-S bonds with electron transfer reagents. Ris[(phenylthio)-methyllsilanes synthesized by the reaction of dichlorosilanes with [(phenylthio)methyl]lithium were transformed to the corresponding bis(lithiomethy1)silanes 7 by reaction with lithium naphthalenide (LiClJ18) or lithium p,p'-di-tert-butylbiphenylide (LiDBB) as an electron transfer reagent and were IntroductionDilithioalkanes can be classified as l,l-, 1,2-, 1,3-, 1,4-etc. dilithio compounds by the position of the lithio substituents in the alkyl chain. In contrast to the large number of dilithioalkane compounds, only a few examples of 1,3-dilithioalkane compounds have been described"]. The 1,3-dilithio compounds exhibit enormous synthetic potential as bifunctional building blocks, e.g., for the synthesis of cyclobutane derivatives. These important synthetic building blocks are not available mainly due to the lack of synthetic routes. Also the decomposition by p-elimination of LiH (e.g., 1,3-dilithiopropane decomposes at -60°C to allyllitihiurn[*]) prevented their preparation ['].As a part of our systematic studies['.3] on the structural unit "-CR2-El-CRZ-" (El = element of group 14-16, partly with substituents; R = H, alkyl, aryl) we have investigated the synthesis of bis(1ithiomethyl)silanes with the structural unit "LiCH2-SiR2-CH2Li" (SiR2 = El). The silicon atom stabilizes the lithio substituent in a-po~ition [~] and prevents a p-elimination reaction.Alkyllithium compounds can normally be prepared by[']: 1. hydrogen-lithium exchange with lithium or lithium bases; 2. halogen-lithium exchange with lithium or lithium bases; 3. metal-lithium exchange with lithium or lithium bases; 4. reductive addition of lithium or lithium bases; 5. reductive cleavage of C-S bonds with lithium. Potential synthetic routes for the synthesis of 1,3-dilithiated compounds are the metal-lithium exchange and the reductive cleavage of C-S bonds.For the synthesis of the two known bis(lithiomethy1)silanes. the halogen-lithium exchange (for S5]) and the reductive cleavage of C-S bonds with lithium {for 4r61) have been used (see Scheme lm). 2 was obtained only in 30% yield due to the elimination of LiCl after monometallation. The only high-yield preparation by Bickelhauptr61 is for the derivative LiCHPh-SiMez-CHPhLi (4), which is n-stabi-

Tris(lithiomethyl)silanes, RSi(CH2Li)3, and tetrakis(lithiomethyl)silane, Si(CH2Li)4, were prepared by the reductive C−S bond cleavage with lithium p,p‘-di-tert-butylbiphenylide (LiDBB) and characterized by trapping with Bu3SnCl. The yields of the isolated trapping products were 42−81% (>95% NMR yield of the crude product), indicating a high-yield synthesis of the corresponding poly(lithiomethyl)silane building blocks. Tetrakis(lithiomethyl)silane is the first compound containing four lithioalkyl groups without any stabilization of the metalated carbon atoms by π-systems. Tetrakis(lithiomethyl)silane was used for the synthesis of 2,2,3,3,7,7,8,8-octamethyl-2,3,5,7,8-pentasilaspiro[4,6]nonane (10), a new spirocyclic disilane. The single-crystal X-ray diffraction study of 10 indicates two five-membered rings in envelope conformation with ecliptically arranged methyl groups connected to a spiro compound by a central silicon atom. DFT geometry optimizations [B3LYP/6-31G(d) level] and NMR calculations (GIAO method, HF/6-31+G(d,p) level) of 10 confirm the observed conformation of 10 as an energetic minimum and support the experimental results.

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