Amine catalyzed reaction

Some authors use O] instead of cr as the substituent constant in such correlations.) An example is provided by the aminolysis of phenyl esters in dioxane the substrates RCOOPh were reacted with -butylamine, and the observed first-order rate constants were related to amine concentration by = k2 [amine] kj [amine]. The rate constants kz and k could be correlated by means of Eq. (7-54), the reaction constants being p = +2.14, b = + 1.03 (for A 2) and p = -1-3.03,8 = -1-1.08 (for ks). Thus, the two reactions are about equally sensitive to steric effects, whereas the amine-catalyzed reaction is more susceptible to electronic effects than is the uncatalyzed reaction. 

The number of reactions that fit into this second class are manifold. Some typical examples are the amine-catalyzed reactions of 2,4-dinitrochlorobenzene with n-butylamine in chloroform (k"/k = 2.59 l.mole-1)23, with allylamine in chloroform (k"jk — 4.60 l.mole-1)24 and with allylamine in ethanol (k"fk =0.36 l.mole-1)25 and the amine-catalyzed reaction of p-nitrofluorobenzene with piperidine in polar solvents (k"/k < 3.2 l.mole-1)26. A typical example of a strongly catalyzed system is the reaction of 2,4-dinitrophenyl phenyl ether with piperidine in 60 % dioxan-40 % water27. 

FIGURE 3.20 Protection of carboxyl groups by esterification of V-protected amino acids (A) by reaction of the anion with an alkyl halide or haloalkyl resin (R = resin) in dimethylformamide51 and (B) by tertiary amine-catalyzed reaction of a symmetrical anhydride with hydroxymethylphenyl-resin (R = resin).53 The intermediate is probably that depicted in Figure 3.19. Reaction (A) is applicable also to the carboxyl groups of peptides. 

The preparation of furyl phosphorodichioridate is based upon a method to prepare 2-chlorofuran (16% yield, Hormi, Nasman unpublished). Later the preparation was extended to a general method to prepare furyl esters from carboxylic acid chlorides lacking a-hydrogens and alkyl furyl carbonates from primary (other than methyl) and secondary alkyl chloroformates. Phosphoryl chloride was the only acid chloride except carbon analogues found to give a furyl ester by the amine-catalyzed reaction. 

The carbon nucleophiles in amine-catalyzed reaction conditions are usually rather acidic compounds containing two electron-attracting substituents. Malonic esters, cyanoacetic esters, and cyanoacetamide are examples of compounds which undergo condensation reactions under Knoevenagel conditions.115 Nitroalkanes are also effective nucleophilic reactants. The single nitro group sufficiently activates the a hydrogens to permit deprotonation under the weakly basic conditions. Usually, the product that is isolated is... 

However, it is also possible that other reaction pathways are involved. For example, in the reaction between M2(NMe2)6 compounds (M = Mo and W) and Me3SiCl (equation 84)181 an amine-catalyzed reaction sequence appears to be operative (equation 85).18... 

Tertiary amine catalyzed reactions proceeded by a general base catalyzed mechanism. 

Other cyclic monomers have been prepared and polymerized through fast ROP. The main focus has been first on bisphenol A carbonate oligocyclic monomers (Brunelle et al., 1994). The oligocyclic monomers were prepared using an amine-catalyzed reaction of bisphenol A bischloroformate, via an interfacial hydrolysis/condensation reaction that also produces linear oligomers and polymers, depending on the structure and concentration of the tertiary amine (Aquino et al., 1994, Table 2.28). 

An impressive addition to the now extensive repertoire of amine-catalyzed reactions is the epoxidation of a-/ -unsaturated aldehydes described by Jorgensen and co-workers, catalyzed by proline-derivative 31 (Fig. 12.11) [77, 78]. As with related processes, this chemistry likely proceeds via activation of the unsaturated alde-... 

C. Enamine vs Enol Pathways in Amine-catalyzed Reactions.1104... 

The KIEs for scission of the C—C bond to form the enamine (by measuring 45C02/44C02 ratios) of both the model amine and the acetoacetate decarboxylase catalyzed reactions were studied by O Leary and Baughn125. In the primary amine catalyzed reaction the KIE exhibited pH-dependence consistent with the kinetic data above. In the enzyme catalyzed reaction a pH independent k12/k13 KIE of 1.018 was reported, consistent with the idea that a nucleophilic attack by the lysine amino group and decarboxylation are both partially rate-limiting. 

Silicon tetrachloride is made by chlorination of Si at red heat. Hexachlorodisilane (Si2Cl6) can be obtained by interaction of SiCL, and Si at high temperatures or, along with SiCL, and higher chlorides, by chlorination of a silidde such as that of calcium. The higher members, which have highly branched structures, can also be obtained by amine-catalyzed reactions such as... 

In a closer study of the amine-catalyzed reaction of phenyl isocyanate with alcohols in toluene solution, Burkus 38) found that contrary to Baker s results observed in dibutyl ether solution, the second-order rate constant was not a linear function of the triethylamine concentration. 

Iwakura and Okada 64) interpret the mechanism and kinetics of the fert-amine catalyzed reactions of isocyanates with n-butanethiol and n-dodecanethiol somewhat differently. They found that the catalyzed reaction was strictly first order with respect to the thiol, isocyanate, and... 

Tertiary amine catalyzed reactions were also studied by Tanaka and Kakiuchi (8), who essentially supported the Fischer mechanism, but disagreed on the kinetic order. The copolymerization kinetic scheme proposed by both Fischer and Tanaka postulate three rates, R, R2, and R, as follows ... 

Figure 7. The effect of triphenyl phosphine on the rate of tin-amine catalyzed reaction of PhNCO with water. Kev O, DBTDL -f- DMEA X, DBTDL - DMEA + Ph.,P , DBTDL. PhNCO = 0.07NI H.O — 0.035M solvent dioxane, 30°C.

Carbon isotope effects for both the amine-catalyzed reaction and the enzyme-catalyzed reaction are significantly different from unity but smaller than those expected if decarboxylation is fully rate determining (99). Thus, in both cases Schiff base formation and decarboxylation must be jointly rate limiting and the enzyme must have accelerated both steps by similar amounts. 

The formation of phosphate esters from amine-catalyzed reactions between dialkyl phosphites and ketones often accompanies the expected production of (a-hydroxyalkyl)phosphonic acid esters (see Section 2.1). It is also known that under... 

The decarboxylation of y8-keto acids by both primary amines and by acetoacetate decarboxylase has been studied by the method of carbon isotope effects [90,91]. A typical isotope effect for the amine-catalyzed reaction is 1.03 for the cyanomethylamine-catalyzed decarboxylation of acetoacetate at pH 5.0. This demonstrates that the carbon-carbon bond is being cleaved in the rate-determining decarboxylation step. The comparable carbon isotope effect for the enzymatic decarboxylation is = 1.018 and is pH-independent over the range pH... 

In pyridine solutions, the statistically corrected relative catalytic coefficients of tertiary amines for 1-methylindene isomerization decreased in the order24 4. quinuclidine, 80 DABCO, 10 triethylamine, 1. The smaller catalytic effectiveness of DABCO than quinuclidine is attributable to its weaker basicity is —30eu for each of these bicyclic bases. On the other hand, triethylamine is about as basic as quinuclidine, but must lose considerable rotational freedom in the rate-limiting proton transfer. This is reflected in the more negative entropy of activation (—39eu) for the triethyl-amine-catalyzed reaction. In pyridine solution, there is a close correlation between pa s of the catalyzing base and A// for 1-methylindene isomerization. Asymmetric catalysis was demonstrated in the quinine-catalyzed isomerization of optically active 1-methylindene in pyridine at 25°C the dextrorotatory indene isomerized nearly twice as fast as its enantiometer247. 

A number of preparatively useful reactions are variants of the mechanistic pattern established by the aldol condensation. One important group is a family of condensations that effect transformations quite similar to the aldol, but that are particularly effectively catalyzed by amines or buffer systems containing amines and the corresponding conjugate acid. These amine-catalyzed reactions are often referred to as Knoevenagel condensations. ... 

The most likely mechanism of the MBH reaction catalyzed by tertiary phosphines is identical to that of the amine-catalyzed reaction except that the initially formed zwitterion 13 can isomerize to phosphorus ylide 14, which can then undergo a Wittig reaction to give olefins 15 (Scheme 1.5). The latter process may require elevated temperatures, since it is not observed in reactions such as the (aza)-MBH reaction involving the more reactive a,p-unsaturated ketones under mild conditions. 

The tertiary amine-catalyzed reactions cause branching and cross-linking and are primarily used for polyurethane foam formation. They are used to accelerate the isocyanate-hydroxyl reaction and give off carbon dioxide. Triethylenediamine is the most prevalent of the tertiary amine catalysts used for polyurethane manufacture. 

Farkas A, Strohm PF (1965) Mechanism of Amine-Catalyzed Reaction of Isocyanates with Hydroxyl Compounds. Ind. Eng. Chem. Fundam. 4 32-38. 

Several mechanisms have been proposed, but very few authors have shown that the orders in reactants depend on the nature of the reaction medium, although Madec and Mar6chal, studying the benzoic/1,2-epoxy-3-phenoxypropane system found that the overall order is 2 in xylene, chlorobenzene, and orthodichlorobenzene as solvent the authors suggested a bimolecular process. However, compared to the amine-catalyzed reaction, the reaction is very slow. 

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