Catalysts amines

Water hydroly2es pure diketene only slowly to give acetoacetic acid [541-50-4] which quickly decomposes to acetone and carbon dioxide, but increasing the pH or adding catalysts (amines, palladium compounds) increases the rate of hydrolysis. The solvolysis of diketene in ammonia results in aceto acetamide [5977-14-0] if used in stoichiometric amounts (99), and P-arninocrotonarnide [15846-25-0] if used in excess (100). 

Imide-terminated telechelics are also synthesized by metathesis depolymerization, and it is found that phthalimide-substituted olefins allow for productive depolymerization when only one methylene spacer separates the nitrogen atom and the olefin (Fig. 8.21). This combination of steric hindrance around the nitrogen lone pair and decreased electron donation from resonance prevents the negative neighboring group effect. However, secondary acyclic amines are unable to produce telechelics through metathesis depolymerization because of unfavorable catalyst-amine interactions. 

Dimerization of methylketene is catalyzed by an amine, trimethylsilylquinine, to give the P-lactone enantioselectively (Scheme 27) [129]. The catalyst amine attacks the ketene to form an ammonium enolate, an electron donating alkene. The donor is strong enough to react with a ketene across the C=0 bond. That is why the P-lactone is obtained instead of the 1,3-cyclobutandione, the uncatalyzed dimerization product of the monosubstituted ketene. 

Ranu and Banerjee developed a [bmim][OH] TSIL for oxidative homocoupling of terminal alkynes to 1,4-disubstituted 1,3-diynes in atmospheric conditions using Cu(ii) without using either palladium catalyst, amines, oxidants or organic solvents. Significant advantages stated by the authors include fast kinetics, high yields and mild reaction conditions. 

Cinchona alkaloids, naturally ubiquitous /3-hydroxy tertiary-amines, are characterized by a basic quinuclidine nitrogen surrounded by a highly asymmetric environment (12). Wynberg discovered that such alkaloids effect highly enantioselective hetero-[2 -I- 2] addition of ketene and chloral to produce /3-lactones, as shown in Scheme 4 (13). The reaction occurs catalytically in quantitative yield in toluene at — 50°C. Quinidine and quinine afford the antipodal products by leading, after hydrolysis, to (S)- and (/ )-malic acid, respectively. The presence of a /3-hydroxyl group in the catalyst amines is not crucial. The reaction appears to occur... 

Typical catalysts are Pd(diphos)2 and RuH2(PPh3)4, while Et3N is a representative co-catalyst amine. 

Organic halide Catalyst Amine Reaction conditions Product i% yield)... 

Catalyst Amine Amine/ catalyst Conversion [%] > Reaction product p [MPa] T[°C] t[h] Ref. 

In tetrahydrofuran, dioxane or amines as the solvent, with ratios of catalyst amine of about 1 20-1 100 at 150-190 °C and under pressures of 1-2 MPa in 6-8 h, conversions of between 20 and 50 % were obtained [5, 6, 8]. As a side reaction, disproportionation of the secondary amines was observed. 

Typical catalysts are Pd°-phosphine complexes, e. g., Pd[P(C6H5)3]4, or in situ catalysts such as Pd(OAc)2/n PlCeHsls, with n = 2...4 (OAc = acetate). Heck and Spencer noticed that phosphines are necessary to somehow stabilize the catalysts. Amines (e. g., N(C2H5)3) are the most common bases but K2CO3, NaHC03, and NaOAc are also applied. The most frequently used catalyst is an in situ combination of Pd(OAc)2 and P(C6H5)3. 

By now this basic formulation has had many interpretations. For example (Activity) has been used to refer to coke-on-catalyst, amine index of the material, reference to conversion in some specific chemical test who knows what else. The value of n, reported in various studies as ranging from 0 to 12, has been represented to indicate diffusion control (0.5) up to essentially "... we don t know what is going on here. .. (12). .. ". The factor is a proportionality constant specific to catalyst, operating conditions and chemical reaction. Voorhies model, based on time-on-stream observations, is obviously not general, but it is a good place to start. 

Derivation A polyether such as polypropylene glycol is treated with a drisocyanate in the presence of some water and a catalyst (amines, tin soaps, organic tin compounds). As the polymer forms, the water reacts with the isocyanate groups to cause cross-linking and also produces carbon dioxide, which causes foaming. In other cases, trifluoromethane or similar volatile material may be used as a blowing agent. 

Thus, by the propoxylation of DETA with around 8-10 mols of PO/mol of DETA, by using dimethylethanolamine as catalyst, aminic polyols of low hydroxyl number (390-420 mg KOH/g) are obtained, with low viscosity of around 6,000-9,000 mPa-s, at 25 °C [1,10,11] ... 

Curitbane . [Air ProdsyPolyurethanes] liq. catalysts amine curing agent for polyurethane intermediate in mfg. of polyamides, pdyimides, coatings, plastics. 

Hartwig s solution to aryl triflate animation was by slow addition of the aryl triflate to a solution of Pd(DPPF) catalyst, amine, and NaOf-Bu.32 This procedure works well for primary amines and secondary cyclic amines, but yields can be lower if the aryl triflate contains R1 = Me or is base sensitive. 

Isocyanates and ureas. In the presence of DMAP as a catalyst, amines form isocyanates at room temperamre. On prolonged reaction, ureas are obtained. Unsymmetrical ureas can be synthesized by adding a second amine to the reaction mixture after 10-20 minutes at room temperature." ... 

By reacting ajnmonia and alcohols in the presence of hydrogenation catalysts, amines are formed. They are also obtained from aldehydes and ketones in nearly the same conditions, if hydrogen is fed simultaneously. 

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