Nucleophilic Catalysis by 4‐(Dialkylamino)pyridines Revisited—The Search for Optimal Reactivity and Selectivity

Abstract

A complex interplay between catalyst structure, acylating agent, auxiliary base, and solvent governs the reactivity and selectivity in 4‐(dialkylamino)pyridine‐catalyzed esterification reactions (see scheme). This highlight attempts a rationalization of the complicated mechanism and puts forward some explanations for seemingly contradictory experimental observations.

Immobilization of Organic Catalysts: When, Why, and How

“…[37] Of the several examples of DMAP analogues anchored on insoluble supports, [4] Tomois polystyrene-supported catalyst 5 (Figure 4), originally reported in 1982 for the acetylation of hindered alcohols, [38] has been recently rediscovered and applied in different types of Baylis-Hillman reactions. [39] For instance at a loading of 20 mol % in DMF, compound 5 promoted the condensation between 4-nitrobenzaldehyde and 3-buten-2-one (MVK) in DMF at 20 8C in 89 % yield [Scheme 2, Eq.…”

Fluorous 4‐N,N‐Dimethylaminopyridine (DMAP) Salts as Simple Recyclable Acylation Catalysts

“…Benzylic alcohols (1-phenylethanol, 1-indanol) underwent facile esterification with both anhydrides within 17 h. After removal of the acid released and precipitation of the catalyst, the corresponding products were afforded with excellent purity and in excellent yields (89-97 %; Table 2, entries 1-4). Aliphatic alcohols, dodecanol and cyclohexanol, also behaved very well and full conversions were obtained within 17 and 8 h, respectively, (85-98 % yield; Table 2, entries [5][6][7][8]. Even the tertiary alcohol 1-methylcyclopentanol was a suitable partner in this reaction, but reacted more sluggishly: warming the reaction mixture to 60 8C for 24 h was required to obtain a good conversion (68-70 % yield; Table 2, entries 9 and 10).…”

“…Thus, remarkable developments are regularly reported, as exemplified by the emergence of more potent analogues, even chiral, [4,5] as catalysts for a diverse range of reactions. [6] Unfortunately, these powerful organocatalysts exhibit acute dermal toxicity, [7] whereas the corresponding salts only produce local irritation by skin contact. [8] To avoid dissemination of these harmful chemicals in the environment, recyclable 4-aminopyridines have been prepared through immobilization on organic or inorganic supports.…”

DMAP as an Effective Catalyst To Accelerate the Solubilization of Waste Fiber‐Reinforced Plastics

“…[11] With this method, waste FRPs were completely solubilized and readily separated into polymeric materials, inorganic additives, and organic monomeric compounds. We have successfully used these reaction products to produce new plastics.…”