Lithiated Methanes

The lithiated methanes have been investigated calculationally already ten years ago by Schleyer, Pople et al. The most exciting result is the decrease of the energy differ-... 

Table 1. Calculated Planar-Tetrahedral Energy Differences (kcal/mol) for Lithiated Methanes (RHF) >...

In a specific example in the same paper [17], one polymer contained triphenyl-methane fragments and the other o-nitrophenol moieties (A and B, respectively, in Scheme 5.1). The triphenylmethane residues were reacted with an alkyllithium and converted to surface-confined trityllithium species. This derivatized polymer was then mixed with an excess of the second polymer and the combination was used in the stoichiometric benzoylation of y-butryrolactonc (Scheme 5.2) or of phenylace-tonitrile (Scheme 5.3). The procedure was also demonstrated successfully using solid sodium hydride instead of the lithiated polymer. 

On the contrary the triphenylsilyl and triphenylgermyl group seem to have no acidifying effect. Lithiation in this case was neither possible with lithiumdicyclohexylamide plus HMPA nor with n-butyllithium or t-butyllithium plus HMPA. In this context it is noteworthy that bi trimethylsilyl)methane 42a) in contrast to bis(triphenylsilyl)methane reacts with n-butyllithium smoothly to the lithium compound The striking difference is well understandable if assuming in bis(tri-phenylsilyl)methane the resonance formulated in Scheme 52 because this brings a... 

Treatment of tri-(2-thienyl)methane with BunLi in the presence of TMEDA in THF at — 78°C gives exclusively the tri-(2-thienyl)methyllithium (393) (96%) without any nuclear lithiation (92CL703). This lithiation is faster than that of triphenylmethane. Treatment of (393) with primary alkyl halides leads to alkylation at the carbanion center, forming (394). However, secondary alkyl halides give mixture of (394) and (395). 

The lithiation-substituton methodology was further extended for meso-functionalization of other bis(furan-2-yl)methane 263, using n-BuLi and dimethyl sulfoxide as solvent additives (Scheme 102). The approach was also extended for C-5 functionalization of bis(furan-2-yl)methane (08TL6234). 

Synthesis of meso-functionalized bis(thien-2-yl)methane 265 (Scheme 103) was reported (10T3682) through lithiation-substitution methodology using dimsyl anion as a base. This approach also furnished meso-linked bis(thien-2-yl)methane derivatives. 

Methyl lithium, butyl lithium, /e/7.-butyl lithium1, and phenyl lithium2 cleave one Te—CH2 bond in bis[phcnyltelluro]methane. However, lithium diisopropylamide lithiates the methylene group rather than breaking a Te-CH2 bond1. 

Zirconocene methyl amide complexes 1 are readily prepared by addition of lithiated secondary or N-silyl amines to zirconocene methyl chloride [17] or zirconocene methyl triflate [18] (Eq. 1). Loss of methane from 1 yields zirconaaziridines which, in the presence of THF or PMe3, can be isolated as the adducts 2 in high yield and purity. This synthetic method is ideal when the isolation and characterization of the resulting zirconaaziridine is desired, as the C-H activation and concomitant methane evolution occur with the formation of little side product. 

Bis(pyrazol-l-yl)methane, kinetic and thermodynamic lithiation, 56, 185 l,l-Bis(pyrazol-4-yl)prop-2-yne, 56, 34 Bis(trifluoromethylsulfonyl)imide, N-fluoro-, fluorination by, 59, 4 Bis(trifluoromethyl)tellurium,... 

Lead(II) chloride reacts with lithiated dimethylamino(ferrocenyl)methane to give (157). In the solid state, the complex exists in the meso form, but in solution it rapidly converts to a mixture of both the meso and rac forms." The general area of intramolecular coordination chemistry of tethered [C,X] donor ligands has been reviewed." ... 

In studies directed toward intermediates for the synthesis of quadrone, Livinghouse demonstrated the utility of lithiated methoxy(phenylthio)(trimethylsilyl)methane (327) for the conversion of aldehydes and ketones to ketene 0,5-acetals (328) in good to excellent yields (Scheme 46). These Peterson alkena-tions gave predominantly the ( )-double bond isomer. As the example depicted in the scheme demonstrates, this procedure may be used to homologate a carbonyl to the phenyl thioester (329) in excellent yields. 

Structures of the Lithiated Tris(aminosilyl)methanes and -silanes... 

The methyne proton of tris(pyrazolyl)methane is sufficiently acidic to be removed by raBuLi, and the resulting reactive intermediate readily reacts with electrophiles. Klaui prepared two new anionic tripodal nitrogen water-soluble ligands (the lithium salts of tris(pyrazolyl)- and tris(3-tert-butylpyrazol)-methanesulfonic, Tpms and Tmps B" respectively) by addition of lithiated tris(pyr-azolyl)methane to a sulfur trioxide-trimethylamine complex (Scheme 25).146... 

Similarly, trimethylsilylcyclopropanes 3 can be formed by addition of lithiated phenylsul-fanyl(trimethylsilyl)methane to activated alkenes. Here, elimination of lithium ben-zenethiolate takes place without further activation. 

Bis(diisopropylamino)phosphanyl(trimethylsilyl)diazomethane 6, easily available by treatment of chlorobis(diisopropylamino)phosphane with lithiated diazo(trimethylsilyl)methane, provides upon flash thermolysis at 250"C the so-called stable carbene 7.38,39,40 behaves partly as a nucleophilic carbene and reacts only with electron-deficient alkenes such as methyl propenoate or diethyl fumarate under cyclopropanation." In the former case only the Z-isomer 8 is formed. Cyclopropane 9 is thermally unstable and is, therefore, oxidized in situ at the phosphorus atom with elemental sulfur to provide cyclopropane 10, Cyclopropanes 8 and 9 are also generated from the diazo compound 6 and the appropriate alkene by photolysis." ... 

Lithiation of bis(2-pyridyldimethylsilyl)methane with BuLi in ether and treatment with carbonyl compounds furnish alkenylsilanes in good yields. ... 

---