Addition reaction of unsaturated compounds

As mentioned previously, although the benzene ring is unsaturated it is generally very stable and does not give the typical addition reactions of unsaturated compounds. Its reactions are generally substitution reactions. 

R. C. Fuson, Reactions of Organic Compounds, Wiley, 1962. Ch. 17, Addition Reactions of Unsaturated Compounds. ... 

Grignard reagents are also synthesized by addition reactions of alkynes, addition reactions of unsaturated compounds having C=S groups, reactions of cycloalkanes, reactions with organolithium compounds or organomercury compounds, etc. [4,15,27,28],... 

Kharasch and Mayo (1959) have shown that the presence of oxygen or peroxides can greatly influence the speed and course of addition reactions of unsaturated compounds. In the absence of oxygen and peroxides HBr adds slowly to allylbromide to yield 1,2-dibromopropane. In the... 

The 1,4-addition reaction of unsaturated carbonyl compounds with Ph3Bi smoothly proceeded in the presence of rhodium catalysts (Scheme 54) [67,68]. Interestingly, the reaction can be conducted in a H20/THF mixture under air. Methyl cinnamate, having an OH group on the aromatic ring, was efficiently phenylated without the protection of the OH group. 

Scheme 54 1,4-Addition reaction of unsaturated carbonyl compounds with Ph3Bi...

The increased availability of methods for the preparation of unsaturated sugars107 has stimulated interest in addition reactions of these compounds the use of unsaturated carbohydrate derivatives as precursors for specifically halogenated sugars has been widely exploited. 

The metal-catalyzed addition reaction of organoboron compounds have not yet been well developed, but die reaction of NaBPh4 or arylboronic acids with enones in the presence of Pd(OAc)2 and NaOAc or SbCL, was recently reported by Uemura and his coworkers.2 The reaction was proposed to proceed through the oxidative addition of the C-B bond to the Pd(0) species however, another probable process, the transmetalation to transition metals, may allow a similar catalytic transformation by the use of organoboronic acids. We report here the 1,4-addition reaction of organoboronic acids to oc, J-unsaturated ketones or esters and 1,2-addition to aldehydes or imines catalyzed by a (acac)Rh(CHj=CH2)2/phosphine complex, which may involve the B-Rh transmetalation as the key step. 

Another non-isohypsic transformation, addition of halogens to a double bond, is probably the oldest known reaction of unsaturated compounds. It is widely used for both industrial and laboratory purposes. The products formed, 1,2-dihaloalkanes, are valuable for conversion into vinyl halides (such as vinyl chloride monomers for the production of PVC) or alkynes ... 

The term hydrosilylation is used to describe addition reactions of R3SiH compounds to unsaturated reagents. The industrial importance of alkene hydrosilylation has led to a rapid development in this area. The synthetic scope of these reactions has been reviewed (179,185,187) so, again, we discuss here only the stereochemical and mechanistic aspects. 

Addition reactions involve unsaturated compounds containing double or triple bonds, particularly C=C and C=C. Hydrogenation and reactions of hydrogen halides and halogens with alkenes and alkynes are examples of addition reactions. 

Asymmetric conjugate addition reactions of carbonyl compounds with a, -unsaturated systems are known. The simple amine a-methylbenzylamine 68 acts as both the activator (to give the imine and hence the enamine required for alkylation) and as the chiral auxiliary to effect neutral asymmetric conjugate-addition reactions. " Thus, condensation of (5)-a-methylbenzylamine 68 with 2-methylcyclohexanone, followed by addition of methyl acrylate (and hydrolysis of the product imine), gave the 2,2-disubstituted cyclohexanone 69 with high enantiomeric purity (1.78). 

Table 1 gives an overview of addition reactions to unsaturated compounds. C-C coupling reactions such as Heck, Suzuki and Sonogashira coupling are described in Section 7.4.2. 

This reaction was first reported by Pudovik in 1950. It is a base-promoted nucleophilic addition of organophosphorus anion to alkenes or alkynes and is generally known as the Pudovik reaction. Occasionally, it is also referred to as the Pudovik addition. In addition, since Abramov discovered a similar addition reaction of phosphorus compounds to carbonyl compounds at the same time, the addition of organophosphorus compounds to activated unsaturated systems (e.g., alkenes, alkynes, ketones, aldehydes,and... 

We have cited several examples which illustrate characteristic ionic polymerization reactions of unsaturated compounds, which may be contrasted with the behavior of alkanes, for which the initial ion-molecule reactions usually lead to stable ion products which do not react further. It was therefore of interest to investigate ionic reactions in cyclobutane, the saturated hydrocarbon isomeric with the unsaturated butenes, to establish whether cyclanes could properly be classified in either of these categories. Additional impetus for such a study was provided by radiolysis data on cyclobutane which suggested that the cyclobutane parent ion rearranges prior to reaction. ... 

The same authors also used ESI-MS/MS to study an air-promoted oxidative Heck reaction between arylboronic acids and enamides as electron-rich olefins (Scheme 7.13) [29]. In addition to the conventional Mizoroki-Heck reaction of unsaturated compounds with organic halides or triflates as electrophiles, the use of nucleophilic organometallic reagents, such as organoboron compounds, has... 

A related selectivity problem arises in addition reactions of unsaturated alkyl derivatives. The example shown on the bottom of Figure 1 illustrates that the 1 1 product 6 can only be generated in reasonable yield, if the nucleophilicity of 5 is higher than that of 4 and 6. An estimate for the relative nucleophilicities of olefinic TT systems in such reactions can be derived from the recently determined reactivity ratios of alkenes and alkynes towards arylcarbenium ions. An additional selectivity problem encountered in the reaction of 4 with 5 - compound 6 does not only incorporate a nucleophilic but also an electrophilic center will be discussed in the next section. 

Chlorine and sodium hydroxide are the main products of the industrial chlor-alkali electrolysis that is described as a process example in Section 6.19. Hydrochloric acid is produced by reaction from the elements H2 and CI2 or by the reaction of chloride salts such as, for example, NaCl or CaCl2, with sulfuric acid. Other important sources of HCl are industrial chlorination processes using CI2 as chlorination agent (e.g., chlorination of benzene to form chlorobenzene and HCl or the chlorination of methane to give chloromethane and HCl) or industrial dehydrochlorination processes (e.g., production of vinyl chloride and HCl from 1,2-dichloroethane). The main uses of hydrochloric acid are addition reactions to unsaturated compounds (by hydrochlorination or oxychlorination), formation of chlorine in the Deacon process, production of chloride salts from amines and other organic bases, dissolution of metals, regeneration of ion exchange resins, and the neutralization of alkaline products. 

The composition of an oil and the progress of its hydrogenation is expressed in terms of its iodine value (IV). Edible oils are mixtures of unsaturated compounds with molecular weights in the vicinity of 300. The IV is a measure of this unsaturation. It is found by a standardized procedure. A solution of ICl in a mixture of acetic acid and carbon tetrachloride is mixed in with the oil and allowed to reac t to completion, usually for less than I h. Halogen addition takes place at the double bond, after which the amount of unreacted iodine is determined by analysis. The reaction is... 

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