Dicarbanionic equivalent

Condensation of benzaldehydes with benzotriazole in the presence of thionyl chloride readily gives a,a-/fe(benzo-triazol-l-yl)toluenes 727 that can be considered as l,l -gm-dicarbanion equivalents. Thus, treatment of derivatives 727 with ketones and lithium metal suspended in THF at — 78 °C generates substituted propylene glycols 728 (Equation 18) <1998TL2289>. 

Oxidocycloheptanones. A soln. of l,3-bis(trimethylsiloxy)-l-methoxy-l,3-buta-diene (as 1,3-dicarbanion equivalent) in methylene chloride treated sequentially with 1 eq. TiCl4 and startg. ketoaldehyde in the same solvent at - 78° product. Y 66%. F.e. incl. 3,7-oxidocyclooctanones, also with diketones and ketoacetals as biselec-trophile, s. G.A. Molander, S.W. Andrews, Tetrahedron Letters 30, 2351-4 (1989). 

A different sequential DreM pathway involving O-carbamate ring switch-vinylogous tolyl amide cydization, 170 —> 171 —> 172 (Scheme 44), a formal bridging of a 2,2 -methyl diaryl dicarbanion with a carbonyl dication equivalent (173) has been affirmed in a model study (174 —> 175, Scheme 45) [73] and applied in natural product total synthesis [73, 74]. 

Compounds of the Type CH3CO—CHa—CO— Can Give Up Two Protons, if treated with 2 equivalents of a strong enough base, to give dicarbanions ... 

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