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Neat reactions

A reaction under neat conditions, with or without catalyst, avoiding the use of organic solvents in the entire operation, including isolation and purification, is of great significance in the design of a green process for industrial application. [Pg.206]


Another AMPA-derived procedure took advantage of the neat reaction between the N-carbamoyl-HHT 59 and diethyl phosphite catalyzed by boron trifluoride etherate to generate the AMPA carbamate 60. Subsequent alkylation with ethyl bromoacetate and base produced the glyphosate triester carbamate 61, which was hydrolyzed to GLYH3 (59). [Pg.28]

The chemistry and toxicology of nitrosamines have been adequately reviewed by Magee et al (1976), Mirvish (1975), Douglas et al (1978) and Fridman et al (1971). The problem of eliminating nitrosamines occurring as trace contaminants in pesticide formulations is markedly different than that of dealing with neat reactions of a given nitrosamine. [Pg.365]

Using day supported ammonium nitrate (dayan), selective deprotection of methoxyphenyl methyl (MPM) ether has been achieved recently using microwave irradiation in solvent-free conditions (Scheme 6.15) [56]. The same reagent has been used for the cleavage of tetrahydropyranyl (THP) ethers. A similar selective preparation and deavage of THP ethers has been achieved under microwave irradiation catalyzed by iodine [57] or neat reaction in an ionic liquid [28],... [Pg.190]

The hetero-DA reaction with azadienes, a well known synthetic method for obtaining nitrogen heterocycles, suffers from some difficulties, because of the low reactivity of the diene. For example, azadiene 2 did not react with DMAD under the action of conventional heating [22], Sequential exposure to MW irradiation (30 W) for 10 min on a graphite support (Tmax = 171 °C) led to the adduct 7 with 60% conversion (50% in isolated product) [26, 27]. An equivalent yield was obtained by ultrasonic irradiation of the neat reaction mixture at 50 °C for 50 h [29]. [Pg.222]

An alternative to the use of supported reagents is the use of uncatalyzed neat reactions . Under these conditions the radiation is absorbed directly by the reagents and this results in spectacular acceleration, higher yields and purity of the reaction products, a simple workup procedure, and sometimes changes in the selectivity of the cycloaddition. [Pg.299]

Dinitrogen tetroxide reacts with simple alcohols in the gas and liquid phase to yield the corresponding nitrite ester as the major product together with trace amounts of oxidation products (Equation 3.4). This is the case for neat reactions and those conducted in methylene chloride between subambient and ambient temperatures. [Pg.93]

Another structurally modified guanidine was reported by Ishikawa et al. as a chiral superbase for asymmetric silylation of secondary alcohols [122]. Soon after, Ishikawa discovered that the same catalyst promoted asymmetric Michael additions of glycine imines to acrylates [123]. The additions were promoted in good yield and great asymmetric induction under neat reaction conditions with guanidine catalyst 250 (Scheme 68). The authors deduced that the high conversion and selectivity were due to the relative configuration of the three chiral centers of the catalyst in... [Pg.189]

A remarkable increase in the rate was observed when the reaction was conducted in ionic liquids instead of CH3CN (Fig. 13). The rate increased by 11 times in [BMIM]BF4 and 34 times in [BMIM]PF6. Furthermore, the product yield was significantly enhanced in [BMIM]PF6 (65%), and this value is considerably higher than that in CH3CN (35%) and is comparable to that of characterizing the neat reaction. The enhanced reaction rates in the ionic liquids were attributed to a shift in the equilibrium favoring stabilization of the zwitterionic intermediate. [Pg.192]

Catalyst RNi. Modifying condition room temperature. Substrate ethyl methyl ketone (MEK) (neat), allylalcohol (All) (neat). Reaction condition 95 kg/cm2. b Activity is expressed by percentage of conversion in 30 min. c Activity is expressed by percentage of conversion in 5 min. [Pg.225]

Many microwave-assisted reactions have been described using neat conditions such conditions can be attractive from an environmental and process productivity point of view. Neat reactions may be assisted by the presence of, or by support on, a microwave active solid, such as a zeolite (e.g., a molecular sieve) or Montmorollinite clay. A great deal of processing flexibility is possible using combinations of the above with microwave irradiation inputs of varying intensity. [Pg.359]

The Bose group s prolific applications of the microwave-assisted ketene-imine annelation process suggest that research laboratories everywhere should be able to justify acquisition of microwave equipment to accelerate research programs via the rapid preparation of a variety of new structures. In a process development setting, the microwave technique should find application in the rapid evaluation and optimization of process parameters, such as solvent, reaction concentration (and neat reactions), temperature, time, pressure, the structure of catalyzing bases/acids, rates of addition, and so on. [Pg.363]

The acid catalyzed oligomers were also synthesized in dilute solutions of dimethylsulfoxide (DMSO) and DMF. DMSO proved to be a less attractive solvent due to its odor and the difficulty of removing it from the products. Additionally, products that were typically clear and colorful when produced in DMF emerged as dark, tar-like materials when synthesized in DMSO. When comparing products of neat reactions to complementary reactions performed in dilute solutions, a 2.5 fold increase in molecular weight and degree... [Pg.147]

A range of organic transformations promoted by lithium bromide and triethy-lamine under neat reaction conditions have been reported. As the reagents ben-zaldehyde and triethylamine are liquids, these reactions may not be entirely solvent free, just without an added solvent. The product distribution (or class of reaction) was affected by the solvent used in the reaction work up (Figure 2.14), and therefore a wide range of products can be obtained using a very simple approach. [Pg.33]

Figure 2.12 PtCl2 catalysed cycloisomerization under neat reaction conditions. Figure 2.12 PtCl2 catalysed cycloisomerization under neat reaction conditions.
Water has been shown to be an effective solvent in some chemical reactions such as free radical bromination. Supercritical fluids such as liquified carbon dioxide are already commonly used in coffee decaffeination and hops extraction. However, supercritical carbon dioxide can also be used as a replacement for organic solvents in polymerization reactions and surfactant production. Future work may involve solventless or neat reactions such as molten-state reactions, dry grind reactions, plasma-supported reactions, or solid materials-based reactions that use clay or zeolites as carriers. [Pg.333]

Excess liquid reagents can be used as solvents in neat reactions. Many PTC reactions have been conducted without organic solvents (see Figure 3.17). Conversions can be very fast and efficient, as in the ethylation of indole [61] (Figure 4.20). The esterification of amino acids in melted octadecanol was also an effective solvent-free reaction (Figure 4.21) [62],... [Pg.107]

Formoterol was also prepared through a neat reaction (Figure 4.22). Significantly, the presence of water leads to the formation of undesired regioisomers during the coupling [63]. In another neat reaction, a small amount of dichloromethane was added to decrease viscosity and allow for better mixing... [Pg.107]

In 2004 Alexakis independently reported on similar reaction conditions (Ti(OiPr)4/ Pd C/H2) as Nugent [22b, 23], albeit when using chiral amines, for example, phen ylethylamine (PEA), phenylpropylamine, and so on, to reductively aminate skeleton matching achiral ketones [30]. By doing so, he synthesized a set of five C2 symmet rical secondary amines from aryl alkyl ketones (Figure 7.5). The optimal conditions called for neat reaction conditions, equal molar quantities of the achiral ketone and chiral amine, Ti(OiPr)4 (3.0 equiv), Pd C (0.5 mol%), and 1.0 bar (14.5 psi) H2. No reaction times were reported. [Pg.237]


See other pages where Neat reactions is mentioned: [Pg.480]    [Pg.452]    [Pg.434]    [Pg.155]    [Pg.172]    [Pg.375]    [Pg.93]    [Pg.107]    [Pg.223]    [Pg.346]    [Pg.427]    [Pg.33]    [Pg.41]    [Pg.76]    [Pg.70]    [Pg.149]    [Pg.315]    [Pg.375]    [Pg.75]    [Pg.37]    [Pg.453]    [Pg.852]    [Pg.106]    [Pg.107]    [Pg.167]    [Pg.57]    [Pg.186]    [Pg.206]    [Pg.238]   
See also in sourсe #XX -- [ Pg.46 , Pg.106 , Pg.107 ]




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Neatness

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