Dodecaborate anions of the type B12X122− and B12X11Y2− (X=H, Cl, Br, I and Y=OH, SH, NH3+, NR3+) form strong (Ka up to 106 L mol−1, for B12Br122−) inclusion complexes with γ‐cyclodextrin (γ‐CD). The micromolar affinities reached are the highest known for this native CD. The complexation exhibits highly negative enthalpies (up to −25 kcal mol−1) and entropies (TΔS up to −18.4 kcal mol−1, both for B12I122−), which position these guests at the bottom end of the well‐known enthalpy‐entropy correlation for CDs. The high driving force can be traced back to a chaotropic effect, according to which chaotropic anions have an intrinsic affinity to hydrophobic cavities in aqueous solution. In line with this argument, salting‐in effects revealed dodecaborates as superchaotropic dianions.
Nitriles Q 0520Diastereoselectivity in Addition of Nitrile-Stabilized Carbanions to Schiff Bases and in Subsequent Alkylation Reactions. -The addition of nitrile-stabilized carbanions to Schiff bases is found to proceed with low diastereoselectivity. Subsequent one-pot alkylation takes place with high or low stereoselectivity depending on the nature of R 1 and the alkyl halide used. -(VITEVA*, L.; GOSPODOVA, T.; STEFANOVSKY, Y.; SIMOVA, S.; Tetrahedron 61 (2005) 24, 5855-5865; Inst. Org. Chem., Bulg. Acad. Sci., BG-1113 Sofia, Bulg.; Eng.) -Jannicke 40-100
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