Br0nsted bases

Planar Chiral Ferrocenes as Lewis- or Br0nsted-Base Catalysts.163... 

Complexes like 64 and 65 can act by two general ways either as a Br0nsted-base or as a nucleophilic catalyst, depending on the type of reaction and substrate. However, the exact mechanistic pathway is in a few cases speculative to some extent as the distinction between the two mechanistic routes is sometimes rather difficult. 

Fig. 36 Catalytic cycle for the Br0nsted-base catalyzed addition of phenols, hydrazoic acid, or 2-cyanopyirol to ketenes...

In the proposed mechanism (Scheme 5-38), the lithium naphthoxide acts as a Br0nsted base to deprotonate the phosphite, and the aluminum is a Lewis acid [28]. 

There is no fundamental difference between trimethylamine acting as a Br0nsted base or as a Lewis base, except that in the Br0nsted concept it donates its electrons to a proton electrophile, whereas as a Lewis base it donates its electrons to a Lewis acid electrophile. 

With this goal in mind, we have studied the reaction of silica with a Lewis acid, such as AlBuj, B(CsF5)3, B(C5F5)j, in presence of a Br0nsted base (Section 2.1). We... 

Recent breakthroughs in enantioselective Br0nsted acid and Br0nsted base catalysis (P. M. Pihko, 2005) [le]. 

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