Reaction Components

The combination of MCRs in one pot is not new. It was first introduced by Domling and Ugi who developed a 7-component reaction (7CR), that was basically a one-pot combination of a modified Asinger 4CR and U CR (Scheme 15) [100, 101]. In this 7CR, an a- or (3-bromo/chloro aldehyde 158, NaSH/NaOH, NH3, another aldehyde 161, an isocyanide 166, CO2, and a primary alcohol (solvent) are combined to afford 167 efficiently. However, NaSH/NaOH, NH3 and CO2 are invariable components in this reaction which limits the substitutional diversity (appendage diversity) and thereby the scope of the MCR. 

Copolymer composition can be predicted for copolymerizations with two or more components, such as those employing acrylonitrile plus a neutral monomer and an ionic dye receptor. These equations are derived by assuming that the component reactions involve only the terminal monomer unit of the chain radical. The theory of multicomponent polymerization kinetics has been treated (35,36). 

A process development known as NOXSO (DuPont) (165,166) uses sodium to purify power plant combustion flue gas for removal of nitrogen oxide, NO, and sulfur, SO compounds. This technology reHes on sodium metal generated in situ via thermal reduction of sodium compound-coated media contained within a flue-gas purification device, and subsequent flue-gas component reactions with sodium. The process also includes downstream separation and regeneration of spent media for recoating and circulation back to the gas purification device. A full-scale commercial demonstration project was under constmction in 1995. 

The lowest temperature for the reaction is 857°C but 1100—1300°C is required for acceptable rates. In this range, the two component reactions proceed at about the same rate and the reduction is diffusion controlled (54). Both reactions are reversible and the overall reaction is endothermic, requiting about 5.5 GJ/t Zn (1.2 X 10 cal/short ton Zn) at 1200 K. 

Thiazolines and thiazolidines may also be prepared in this fashion, the structure of the final product determining the substitution pattern to be chosen in the reaction components. Reaction of ethyl bromoacetate with the substituted thioamide (71) resulted in formation of the thiazolidin-4-one (72) (70KGS1621). 

The component reactions in eqn. (2) are very fast, and the system exists in equilibrium. Additional carbon dioxide entering the sea is thus quickly converted into anions, distributing carbon atoms between the dissolved gas phase, carbonate and bicarbonate ions. This storage capacity is clear when the apparent equilibrium constants for the two reactions in eqn. (2) are examined, namely... 

Maintenance or cleaning of equipment Residues Loss of containment (breaking lines) Stripping insulation Burning-off paint, flame heating components Reaction or vaporization of cleaning products... 

The Biginelli reaction involves an one-pot reaction between aldehyde 1, 1,3-dicarbonyl 2, and urea 3a or thiourea 3b in the presence of an acidic catalyst to afford 3,4-dihydropyrimidin-2(l//)-one (DHPM) 4. This reaction is also referred to as the Biginelli condensation and Biginelli dihydropyrimidine synthesis. It belongs to a class of transformations called multi-component reactions (MCRs). 

This shows that the assumption made in Eqs. (18) and (19), i.e., that the Hammett equation is separately applicable to the component reactions, does not imply linearity of a plot of vs. a. The assumption of the applicability of the Hammett equation to the component series seems undeniable since these reactions are extremely closely related to series which follow the Hammett equation very well. This assumption also implies... 

Tlie Ca substituent effects have been experimentally studied by synthesizing and investigating the A -(l,2,2,2-tetrachloroethyl)pyridinium chloride (43). Tlie synthesis of 43 follows the standard three-component reaction. Tliionyl chloride, trichloroacetaldehyde, and pyridine were reacted at 0°C in MeCN to give this salt in excellent yield (Scheme 31). 

Scheme 5.1-43 Three-component reaction of benzaldehyde, aniline, and diethyl phosphonate in ionic liquids, catalyzed by lanthanide triflates and indium(lll) chloride.

The Maunich reaction of a ketone, an amine, and an aldehyde is one of the few three-component reactions in organic chemistry. Cyclohexanone, for example, reads with dimethylamine and acetaldehyde to yield an amino ketone. The reaction takes place in two steps, both of which are typical carbonyl-group reactions. 

In Ugi four-component reactions (for mechanism, see Section 1.4.4.1.) all four components may potentially serve as the stereodifferentiating tool65. However, neither the isocyanide component nor the carboxylic acid have pronounced effects on the overall stereodiscrimination60 66. As a consequence, the factors influencing the stereochemical course of Ugi reactions arc similar to those in Strecker syntheses. The use of chiral aldehydes is commonly found in substrate-controlled syntheses whereas the asymmetric synthesis of new enantiomerically pure compounds via Ugi s method is restricted to the application of optically active amines as the chiral auxiliary group. 

Rule To find any proposed heat of reaction write down the chemical equations of the component reactions so that each symbol appears equally often on both sides of the sign of equality. If the heats of reaction (with proper signs) have been inserted, the unknown heat of reaction being denoted by x then the latter... 

A direct insertion of sulfur dioxide into a C—C bond has been observed under photochemical conditions 3 (equation 72) a related CH insertion followed by an intramolecular sulfinate to carbonyl addition yields the same system 3 (equation 73). A further sulfolene synthesis utilizes a three-component reaction see equation 74 (cf. Section IV below) 35. 

If a chemical equation can be expressed as the sum of two or more chemical equations, the equilibrium constant for the overall reaction is the product of the equilibrium constants for the component reactions. For example, consider the three gas-phase reactions... 

A microwave-assisted three-component reaction has been used to prepare a series of 1,4-disubstituted-1,2,3-triazoles with complete control of regiose-lectivity by click chemistry , a fast and efficient approach to novel functionalized compounds using near perfect reactions [76]. In this user-friendly procedure for the copper(l) catalyzed 1,3-dipolar cycloaddition of azides and alkynes, irradiation of an alkyl halide, sodium azide, an alkyne and the Cu(l) catalyst, produced by the comproportionation of Cu(0) and Cu(ll), at 125 °C for 10-15 min, or at 75 °C for certain substrates, generated the organic azide in situ and gave the 1,4-disubstituted regioisomer 43 in 81-93% yield, with no contamination by the 1,5-regioisomer (Scheme 18). 

The synthesis of functionahzed tetrahydrocarbazoles can be promoted by microwave irradiation [84], The organocatalytic four-component reaction of a solution of 2-substituted indole, aromatic aldehyde (2 equiv) and Mel-drum s acid in benzene in the presence of DL-proline proceeds when heated under Dean-Stark conditions for 5 min in a single-mode microwave reactor to give the tetrahydrocarbazole product as a mixture of diastereoisomers (Scheme 24). 

The use of microwave-assisted multicomponent cycloaddition reactions allows unique heterocyclic scaffolds to be assembled rapidly from readily accessible starting materials. The three-component reaction of M-alkyl-l,4-DHP... 

This is a set of N ordinary differential equations, one for each component. The component reaction rates will have M terms, one for each reaction, although many of the terms may be zero. Equations (2.9) are subject to a set of N initial conditions of the form... 

The extension to multiple reactions is done by writing Equation (3.1) (or the more complicated versions of Equation (3.1) that will soon be developed) for each of the N components. The component reaction rates are found from Equation (2.7) in exactly the same ways as in a batch reactor. The result is an initial value problem consisting of N simultaneous, first-order ODEs that can be solved using your favorite ODE solver. The same kind of problem was solved in Chapter 2, but the independent variable is now z rather than t. 

Fortunately, it is possible to develop a general-purpose technique for the numerical solution of Equation (3.9), even when the density varies down the tube. It is first necessary to convert the component reaction rates from their normal dependence on concentration to a dependence on the molar fluxes. This is done simply by replacing a by and so on for the various... 

In analogy, Ugi et al. reported on a lactam formation by running a one-pot three components reaction the condensation of L-lysine 7, isobutyraldehyde and methyl isocyanide led to the corresponding a-amino-c-caprolactam 9, but the yield was not given. The authors presumed either a nucleophilic substitution of the ester 8 as the primary Ugi product by the amino function of the side chain or, alternatively, the nucleophilic attack of the NH2-group on an intermediately formed 0-acylamide and a subsequent rearrangement (Scheme 1) [4]. 

An alternate approach is to utilize the chromatogram heights as representative of individual concentrations of molecular size. From the kinetic modeling viewpoint, this leads to treating the polymerization as a well-characterized, multi-component reaction system. 

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