Addition-elimination reactions substitution

J 7 Predict the products of given elimination, addition, and substitution reactions (Sections 18.4, 18.6, and 18.8). 

Addition reactions, substitution reactions, and elimination reactions are the three main types of organic reactions. Most organic reactions can be classified as one of these three types. 

Going over the basics and mechanisms of nucleophilic substitution reactions Mastering mechanisms of elimination/addition reactions Determining synthesis strategies for aromatic systems... 

Two other important modes of substitution require mention here. They are the SNAr and elimination-addition reactions. Actually, it is sometimes difficult to distinguish between true aromatic nucleophilic substitutions and addition-elimination processes. The second group involves pyridyne intermediates (Scheme 53). Both of these reaction types are discussed fully under substituent reactions (Chapter 2.06). 

On solid acid—base catalysts, beside elimination, addition and substitution, some other reactions also proceed. Of these, especially skeletal isomerisation of hydrocarbons and double bond shift should be mentioned. The latter can influence the product composition in olefin-forming eliminations and thus distort the information on orientation being sought. 

It seems probable, in view of the idea presented in Sect. 1.1, that, in elimination, addition and substitution reactions over ion exchangers, also, two types of catalytic sites are involved, viz. acidic (protons of the functional groups) and basic, which are likely to be represented by oxygen atoms of the functional groups. 

Condensation of sodium phenoxide with 2,2,2-trifluoroethyl iodide gives a product of direct substitution in a low yield, several other ethers are formed by elimination-addition reactions [7] Use of mesylate as a leaving group and hex amethyl phosphoramide (HMPA) as a solvent increases the yield of the substitution [5] Even chlorine can be replaced when the condensation is performed with potassium fluonde and acetic acid at a high temperature [9] (equations 6-8)... 

An efficient procedure for the nucleophilic displacement of the A, A -dimethylamino group of 1-triisopropylsilyl-gramines via the fluoride ion-induced elimination-addition reaction has been devised. 1-Triisopropylsilylgramine methiodide 1371 reacted smoothly with a variety of nucleophiles in the presence of tetrabutylammonium fluoride (TBAF) to give 3-substituted indoles 1372 (Scheme 262) <1995TL5929>. 

Common Reaction Types and Preparative Aspects A. Addition reactions Substitution reactions Dimerization-addition reactions Dimerization-elimination reactions Cleavages Chain reactions Indirect oxidations Voltammetry and Studies of Kinetics and Mechanisms A. Aromatic hydrocarbons Arylalkenes... 

The problem here is to decide between the elimination-addition and substitution mechanisms of alkylations. Elimination reactions were therefore studied first. 2-Piperidinomethylcyclopentanone (4) and -piperidinopropiophenone (6) were the first Mannich bases examined (Horak et al., 1961). Reactions (2a) and (2b) were expected. Equation (3) is a general formulation. 

A large number of halogenated cyclopropanes have been converted to cyclopropyl sulfides (Table 14) there is one example of the formation of a sulfinic acid. A variety of methods have been used utilizing both nucleophilic and electrophilic cyclopropane species and there are also the possibility of carrying out formal substitution by elimination/addition reactions. 

When halocyclopropanes react with an alkali metal alkoxide in an organic solvent, elimination-addition reactions take place and result in formation of alkoxycyclopropanes. In most cases the overall reaction can be regarded as a simple substitution of a halogen atom by an alkoxy group (see Section 5.2.1.1.11.2.2.), but in some cases a double substitution is observed. The latter reaction occurred when 6,6-dichloro-3-thiabicyclo[3.1.0]hexane was treated with potassium fcr/-butoxide and gave l-tcrt-butoxy-e r/o-6-chloro-3-thiabicyclo[3.1.0]hexane (1) in 68% yield. The reaction is believed to take place via a strained cyclopropene intermediate, which is trapped by nucleophilic attack of the ferr-butoxide or by reaction with furan if present.Other 1,1-dichlorocyclopropanes react analogously under similar conditions, 22-724 jjyj jien an excess of base is used, a second elimination-addition... 

An elimination-addition reaction sequence resulting in formation of a methylselenocyclo-propane by both double and single substitution takes place when endo-l-chloro-la,2,3,7b-tetra-hydro-l//-cyclopropa[fl]naphthaleneis treated with lithium methylselenide in dimethyl sulfoxide in the presence of 18-crown-6. However, the products were obtained in low yields, 17 and 3%, respectively (Section 5.2.1.1.13.). 

Table 3. Selected Examples of Elimination/Addition Reactions of l-Amino-1-acceptor-Substituted Cyclopropanes...

The replacement of the fluorine atoms by chlorine atoms led to the formation of 2,2-dimethoxy-2,3-dihydrofurans 18 as the result of a ring enlargement. As in the difluorocyclopropyl series, the cyclopropane carbon with the geminal halogen substituents reached the oxidation state of a carboxylic acid by a sequence of elimination, addition and substitution reactions of unknown order. 

The incoming nucleophile can attack either of the carbons of the triple bond of benzyne. Protonation of the resulting anion forms the substitution product. The overall reaction is an elimination-addition reaction Benzyne is formed in an elimination reaction and immediately undergoes an addition reaction. 

Lectures 5 + 6 atom economy - rearrangement reaetions, addition reactions, substitution reactions, elimination reactions Lectures 7 + 8 design for degradation - the cost of waste, waste minimization, waste treatment, designed for degradation, and recycling and disposal... 

The benzyne mechanism can be denoted as an Sn(EA) (substitution nucleophilic elimination addition) reaction (reference 7). 

We begin with chlorination of benzene (which is just an electrophilic aromatic substitution reaction), followed by an elimination-addition reaction. When we perform the elimination-addition process, we must carefully choose the reagents. If we use NaOH followed by HsO", the product will be phenol. If we use NaNH2 followed by HsO", the product will be aniline (shown in the scheme above). 

The reactions of organic compounds can be divided into three main types addition reactions, substitution reactions, and elimination reactions. The particular type of reaction a compound undergoes depends on the functional group in the compound. Part 2 discusses the reactions of compounds whose functional group is a carbon-carbon double bond or a carbon-carbon triple bond. We will see that these compounds undergo addition reactions, or, more precisely, electrophilic addition reactions. Part 2 also examines stereochemistry, thermodynamics and kinetics, and electron delocalization—topics that can be important when trying to determine the outcome of a reaction. 

Iwao et d. introduced an efficient methodology ftH the synthesis of 3,4-disubstituted indoles 113 (57). Their strategy comprises two sequential steps 1) selective functionalization of l-silyl-3-dimethylaminomethylindole (111) at the 4-position by directed lithiation, followed by quenching with electrophiles, for the preparation of 4-dimethylamino-substituted indole 112 (58) 2) substitution of the dimethylamino group of 112 for various nucleophiles giving 113 upon desilylation through quatemization followed by a fluoride ion-induced elimination-addition reaction (Scheme 17) (59). 

NaOH SuAror elimination-addition A strong nucleophile used in nucleophihc aromatic substitution reactions as well as elimination-addition reactions. 

Now let s draw the forward scheme. Benzene is converted into chlorobenzene upon treatment with CI2 and AICI3 (via an electrophilic aromatic substitution reaction). Chlorobenzene is then converted to aniline via an elimination-addition reaction. Reaction with acetyl chloride (in the presence of pyridine) converts aniline to the desired amide. 

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