Triethylamine as solvents

Following the key finding of Helmchen [23], the bis-(S)-ethyl lactate ester of fumaric acid was prepared from fumaryl chloride, as illustrated in Scheme 2. Cycloaddition of this dienophile with cyclopentadiene to give (3) required some experimental modification in order to eliminate halogenated solvents. A survey of solvents and reaction conditions revealed that triethylamine as solvent allows both a reasonable reaction rate and high diastereomeric excess (d.e. = 93%) when the reaction is conveniently conducted at room temperature. 

Claisen condensation between an ester and the methylene adjacent to the carbonyl of the acylarene produces a l-(ortft(9-hydroxyaryl)-l,3-diketone. The Claisen condensation can be conducted in the presence of the acidic phenolic hydroxyl by the use of excess strong base triethylamine as solvent and base can also be utilised. " Alternatively, the process is conducted in two steps first, acylation of the phenolic hydroxyl, and secondly, an intramolecular ° base-catalysed Claisen condensation, known as the Baker-Venkataraman rearrangement a synthesis of flavone itself is illustrative. ... 

Tri-O-benzyl-L-galactitol was converted into the isopropylidene mesylate 24. Treatment of 24 with lithium azide in DMF gave the azide 25 with inversion of the configuration. Reduction of the azide 25 with lithium aluminum hydride gave the amine 26 To protect the amino group, N-ethoxycarbonylphthalimide was used with triethylamine as solvent to give the phthaloyl derivative 27... 

Several SP materials have been used for the extraction of FRs from aqueous samples, plasma and milk (Table 31.7). Similar materials have been used for all FRs. Typical SP materials include Ci8 and Cg bonded to porous silica, highly cross-linked poly(styrene divinylbenzene) (PS-DVB), and graphitized carbon black (GCB). It is also possible to use XAD-2 resin for extraction of various FRs, pesticides, and plastic additives from large volumes of water (100 1). The analytes can then be either eluted from the resin by acetone hexane mixture, or Soxhlet extracted with acetone and hexane. For a specific determination of diphenyl phosphate in water and urine, molecularly imprinted polymers have been used in the solid phase extraction. The imprinted polymer was prepared using 2-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate as the cross linker, and a structural analog of the analyte as the template molecule. Elution was done with methanol triethylamine as solvent. Also solid phase microextraction (SPME) has been applied in the analysis of PBDEs in water samples. The extraction has been done from a headspace of a heated water sample (100°C) using polydimethylsiloxane (PDMS) or polyacryl (PA) as the fiber material. ... 

Broad band irradiation of 3,5,6-triphenyl-l,2,4-triazine in neat triethylamine as solvent leads to rapid degradation of the starting material and N-dealkylation of triethylamine to give 2,5-dihydro-3,5,6-triphenyl-l,2,4-triazine, as well as ting-contraction products, 3,5-diphenyl-1,2,4-triazole and 2,3-di(3,5-diphenyl-l,2,4-triazol-l-yl)butane, as a mixture of stereomeric compounds (Scheme 1) <2000MI57>. 

Guanidines have also been employed as catalysts in Michael reactions with enones and, for example, bicyclic guanidine 86 has been found to perform well in the Michael reaction of different 1,3-dicarbonyl compounds with cyclo-pentenones, providing the final Michael adducts with excellent yields and enantioselectivities (Scheme 4.33). In this case, the authors found that the use of triethylamine as solvent resulted in a dramatic increase in the rate of the reaction, without affecting significantly its stereochemical outcome with respect to the same reaction in toluene, which is the usually chosen solvent when working with this type of catalyst. 

Finally, the total red shift of 5380 cm of the solvatochromic band of 4-nitrophenol, on going from the gas phase to acetonitrile solution, has been resolved into a 785 cm hydrogen-bond shift (15% of the total shift) and a 4595 cm shift caused by nonspecific (van der Waals) interactions. With triethylamine as solvent, the hydrogen-bond shift amounts to 42% of the total shift. These examples show the importance of quantifying the Lewis basicity of solvents for a quantitative description of solvent effects in chemistry. 

Fig. 1. Time courses of the chemiluminescence intensity from oxalate—hydrogen peroxide systems in ethyl acetate as solvent, 0.7 mM TCPO. The curves correspond to the following concentrations of triethylamine (TEA) catalyst A, 0.05 mM B, 0.10 mM and C, 0.20 mM (70).

Recently Tanabe and co-workers have found that several alcohols were smoothly and efficiently tosylated using tosyl chloride/triethylamine and a catalytic amount of trimethylamine hydrochloride as reagents.6 Compared with the traditional method using pyridine as solvent, this procedure has the merit of much higher reaction rates, and it avoids the side reaction in which the desired tosylate is converted into the corresponding chloride. 

The alkanephosphonic acid dichlorides obtained by these methods are converted with amines, with all reactions carried out in solvents such as acetone, benzene, or diethyl ether at 10°C with triethylamine as HC1 captor. The conversion runs quantitatively followed by a purification with the help of column chromatography with chloroform/methanol in a ratio of 9 1 as mobile phase. The alkanephosphonic acid bisdiethanolamides could be obtained as pure substances with alkane residues of C8, C10, C12, and Ci4. The N-(2-hydroxyethane) alkanephosphonic acid 0,0-diethanolamide esters were also prepared in high purity. The obtained surfactants are generally stable up to 100°C. Only the alkanephosphonic acid bismonomethylamides are decomposed beneath this temperature forming cyclic compounds. 

This acylation reaction is performed in the presence of triethylamine using DMF or dioxane as solvent [83]. 

Reactions with succinic anhydride or acetic anhydride to block dendrimer amines can be done in aqueous or methanolic solution. If organic solvent is used for the reaction, then it is typical to include triethylamine as a proton acceptor, which helps drive the reaction. Such reactions, however, can t be done to dendrimer amines once a protein containing amines also has been conjugated, as the protein too will get modified. 

Dissolve bis-NHS-PEG5 into the solvent of choice at a concentration of lmg/ml also containing an equal molar concentration of triethylamine as base. Add the crosslinker solution to the surface or to the particles to coat them fully. When working with particles, centrifuge them to remove solvent prior to resuspending in the crosslinker solution. 

The groups of Giacomelli and Taddei have developed a rapid solution-phase protocol for the synthesis of 1,4,5-trisubstituted pyrazole libraries (Scheme 6.194) [356]. The transformations involved the cyclization of a monosubstituted hydrazine with an enamino-/8-ketoester derived from a /8-ketoester and N,N-dimethylformamide dimethyl acetal (DMFDMA). The sites for molecular diversity in this approach are the substituents on the hydrazine (R3) and on the starting j3-keto ester (R1, R2). Subjecting a solution of the /8-keto ester in DMFDMA as solvent to 5 min of microwave irradiation (domestic oven) led to full and clean conversion to the corresponding enamine. After evaporation of the excess DMFDMA, ethanol was added to the crude reaction mixture followed by 1 equivalent of the hydrazine hydrochloride and 1.5 equivalents of triethylamine base. Further microwave irradiation for 8 min provided - after purification by filtration through a short silica gel column - the desired pyrazoles in >90% purity. 

Heck tried the reductive dimerization of isoprene in formic acid in the presence of triethylamine at room temperature using 1% palladium phosphine catalysts to give dimers in up to 79% yield (95). Better selectivity to the head-to-tail dimer was obtained by using Pd(OAc)2 with 1 1 ratio of arylphosphines. THF as solvent showed a favorable effect. In a scaled-up reaction with 0.5 mole of isoprene using 7r-allylpalladium acetate and o-tolyphosphine, the isolated yield of the dimers was 87%. The dimers contained 71% of the head-to-tail isomers. The mixture was converted into easily separable products by treatment with concentrated hydro-... 

Treatment of l-methyltetrazolo[5,l-tf]isoindolium perchlorate 49 with acyl chlorides and triethylamine in dioxane as solvent affords a mixture of the 5-acyl-l-methyltetrazolo[5,l-tf]isoindoles 50 and the monomethine cyanine dye 51 (Equation 2) <2004T195>. 

Reaction of 1,2 -dicarboxylic acids has been used for the formation of a number of strained alkenes and also applied to the Diels-Alder addition products from maleic anhydride (Table 9.5). Both cis- and tr s-diacids take part in the process. Aqueous pyridine containing, triethylamine as a strong base, is considered the best solvent and higher yields are obtained at temperatures of around 80 "C [130]. Use of a divided cell avoids a possibility of electrocatalytic hydrogenation of the product at the cathode. The addition of /a/-butylhydroquinone as a radical scavenger prevents polymerization of the product [127], An alternative chemical decarboxylation process is available which uses lead tetraacetate [131] but problems can arise because of reaction between the alkene and lead tetraacetate. 

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