Doped complex bases, a new consequence of aggregative activation

Abstract

According to the basic principles of aggregative activation, it has been shown that the efficiency of the complex base NaNH2-ButONa can be improved by simple addition of a potassium salt.

Activation of Dimethyl Zirconocene by Methylaluminoxane (MAO)Size Estimate for Me-MAO- Anions by Pulsed Field-Gradient NMR

“…The singlet CH 2 signal of this internal reference compound at 3.80 ppm was used for all diffusion and integral intensity measurements. For this purpose, bis-α,α‘(trityl)-4,4‘-dimethylbiphenyl was prepared in analogy to a procedure previously described, and characterized by 1 H NMR [(C 6 D 6 , δ): 3.80 (s, 4H), 6.67 (d, 4H, 7.8 Hz), 7.00 (d, 6H, 7.2 Hz), 7.04 (t, 12H, 7.2 Hz), 7.08 (d, 4H, 7.8 Hz), 7.22 (d, 12H, 7.2 Hz)] and 13 C NMR [(CDCl 3 , signal intensities determined with inverse gated proton decoupling, δ): 46.29 (CH 2 , 2C), 58.79 (C, 2C), 125.90 (CH, 4C), 126.26 (CH, 6C), 127.91 (CH, 12C), 130.13 (CH, 12C), 131.78 (CH, 4C), 137.62 (C, 2C), 138.56 (C, 2C), 146.91 (C, 6C)]. The chemical inertness of this reference compound toward MAO and MAO/(C 5 H 5 ) 2 ZrMe 2 reaction mixtures in solution was confirmed by separate experiments.…”

Unimetal super bases

“…Another argument supporting a mixed aggregate structure for complex bases is the appreciable rate increase in carbanion formation-electrophilic condensation (vide infra) when potassium halide is added to NaNH2~CB. 22 This result is interpreted as partially due to the formation of a MSB as symbolized in Scheme 13.…”

“…With the AA basic principles as a starting point we undertook a study in an attempt to increase the efficiency of such USB's in proton abstraction-electrophilic condensation reactions. 22 It was found that the simple addition of potassium halides to NaNH2-£-BuONa led to an appreciable (2-3 times, depending on the nature of the salt) increase in the reaction rate. A weak thermodynamic effect was also observed.…”

Mixed AggregAte (MAA): A Single Concept for All Dipolar Organometallic Aggregates. 2. Syntheses and Reactivities of Homo/HeteroMAAs

“…A similar alkylation acceleration of carbanions, generated from Ph 3 CH and Ph 2 CH 2 in the presence of K + -doped H 2 NNa· t -BuONa, was observed by Caubère and co-workers. The latter attributed this result to an “aggregative activation” in which the insertion of cations, different from the ones present in a complex base, increases the aggregates dissymmetry and thus modify the efficiency of reagents …”

“…The latter attributed this result to an "aggregative activation" in which the insertion of cations, different from the ones present in a complex base, increases the aggregates dissymmetry and thus modify the efficiency of reagents. 352 4.1.3. Nu-Mg,Mg-HomoMAAs.…”