Dimethylaminopyridin

Vinylpyridine (23) came into prominence around 1950 as a component of latex. Butadiene and styrene monomers were used with (23) to make a terpolymer that bonded fabric cords to the mbber matrix of automobile tires (25). More recendy, the abiUty of (23) to act as a Michael acceptor has been exploited in a synthesis of 4-dimethylaminopyridine (DMAP) (24) (26). The sequence consists of a Michael addition of (23) to 4-cyanopyridine (15), replacement of the 4-cyano substituent by dimethylamine (taking advantage of the activation of the cyano group by quatemization of the pyridine ring), and base-cataly2ed dequatemization (retro Michael addition). 4-r)imethyl aminopyri dine is one of the most effective acylation catalysts known (27). 

Dimethylaminopyridine [1122-58-3] (DMAP) (24) has emerged as the preferred catalyst for a variety of synthetic transformations under mild conditions, particularly acylations, alkylations, silylations, esterifications, polymeri2ations, and rearrangements (100). POLYDMAP resin [1122-58-3], a polymeric version of DMAP, is available, and is as effective as DMAP as a catalyst for acylation reactions. Furthermore, it can be recycled without regeneration more than 20 times with very Htde loss in activity. POLYDMAP is a trademark of Reilly Industries, Inc. 

However, this method is appHed only when esterification cannot be effected by the usual acid—alcohol reaction because of the higher cost of the anhydrides. The production of cellulose acetate (see Fibers, cellulose esters), phenyl acetate (used in acetaminophen production), and aspirin (acetylsahcyhc acid) (see Salicylic acid) are examples of the large-scale use of acetic anhydride. The speed of acylation is greatiy increased by the use of catalysts (68) such as sulfuric acid, perchloric acid, trifluoroacetic acid, phosphoms pentoxide, 2inc chloride, ferric chloride, sodium acetate, and tertiary amines, eg, 4-dimethylaminopyridine. 

Pyrrole and alkylpyrroles can be acylated by heating with acid anhydrides at temperatures above 100 °C. Pyrrole itself gives a mixture of 2-acetyl- and 2,5-diacetyl-pyrrole on heating with acetic anhydride at 150-200 °C. iV-Acylpyrroles are obtained by reaction of the alkali-metal salts of pyrrole with an acyl halide. AC-Acetylimidazole efficiently acetylates pyrrole on nitrogen (65CI(L)1426). Pyrrole-2-carbaldehyde is acetylated on nitrogen in 80% yield by reaction with acetic anhydride in methylene chloride and in the presence of triethylamine and 4-dimethylaminopyridine (80CB2036). 

Et3SiCl, Pyr. Triethylsilyl chloride is by far the most common reagent for the introduction of the TES group. Silylation also occurs with imidazole and DMF arid with dimethylaminopyridine as a catalyst. Phenols, carboxylic acids, and amines have also been silylated with TESCl. 

AC2O, AcCl, Pyr, DMAP, 24-80°, 1-40 h, 72-95% yield. The use of DMAP increases the rate of acylation by a factor of 10. These conditions will acylate most alcohols, including tertiary alcohols. The use of DMAP (4-N,N-dimethylaminopyridine) as a catalyst to improve the rate of esterification is quite general and works for other esters as well. 

DMAP = 4-dimethylaminopyridine (lO" times more effective than pyri- dine) ... 

PhCH20CO-imidazolyl, 4-dimethylaminopyridine, 16 h, it, 76% yield. Two primary amines were protected in the presence of a secondary amine. 

Oxiranes exhibit 1,3 [e,n] capacity. Therefore, seven-membered ring systems can be synthesized on reaction with hetero-1,3-dienes. The reaction is catalyzed by 4-dimethylaminopyridine. On catalysis with boron trifluonde, the regioche-mistry is reversed [263] (equation 58). 

These rate constants are for the hydrolysis of cinnamic anhydride in carbonate buffer, pH 8.45, total buffer concentration 0.024 M, in the presence of the catalysts pyridine, A -methylimidazole (NMIM), or 4-dimethylaminopyridine (DMAP). In the absence of added catalyst, but the presence of buffer, the rate constant was 0.005 24 s . You may assume that only the conjugate base form of each catalyst is catalytically effective. Calculate the catalytic rate constant for the three catalysts. What is the catalytic power of NMIM and of DMAP relative to pyridine ... 

Disubstituted4-dimethylaminopyridines as artificial inhibitors of transcription factors involved in HIV replication 97YGK697. 

By application of the Corey-Winter reaction,vicinal diols 1 can be converted into olefins 3. The key step is the cleavage of cyclic thionocarbonates 2 (1,3-dioxolanyl-2-thiones) upon treatment with trivalent phosphorus compounds. The required cyclic thionocarbonate 2 can be prepared from a 1,2-diol 1 and thio-phosgene 4 in the presence of 4-dimethylaminopyridine (DMtVP) ... 

Di-tert-butyl dicarbonate and 4-dimethylaminopyridine were purchased from Alfa-Aesar Chemical Company and used without further purification. 

In place of N-methylimidazole (Melm), only dimethylaminopyridine (DMAP) could be substituted. The solid-supported amines piperidinomethyl- or morpholinomethyl polystyrene resins, pyridine, and tertiary amines like triethylamine andN-methylmorpholine were not effective. 

PS-DMAP Polystyrene-hound dimethylaminopyridine Rfs Perfluorooctyl, CsFu... 

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