Aromatic compounds, addition reagents

The reaction has been applied to nonheterocyclic aromatic compounds Benzene, naphthalene, and phenanthrene have been alkylated with alkyllithium reagents, though the usual reaction with these reagents is 12-20, and Grignard reagents have been used to alkylate naphthalene. The addition-elimination mechanism apparently applies in these cases too. A protected form of benzaldehyde (protected as the benzyl imine) has been similarly alkylated at the ortho position with butyl-lithium. ... 

Synthetically important substitutions of aromatic compounds can also be done by nucleophilic reagents. There are several general mechanism for substitution by nucleophiles. Unlike nucleophilic substitution at saturated carbon, aromatic nucleophilic substitution does not occur by a single-step mechanism. The broad mechanistic classes that can be recognized include addition-elimination, elimination-addition, and metal-catalyzed processes. (See Section 9.5 of Part A to review these mechanisms.) We first discuss diazonium ions, which can react by several mechanisms. Depending on the substitution pattern, aryl halides can react by either addition-elimination or elimination-addition. Aryl halides and sulfonates also react with nucleophiles by metal-catalyzed mechanisms and these are discussed in Section 11.3. 

Any nitro- or amino-aromatic compound may be considered a potential source of interference until demonstrated otherwise. For example, DN-111 in benzene was processed in the usual manner. During the reduction step a pink color developed which was insoluble in petroleum ether addition in proper sequence of the dye-producing reagents resulted in the development of a deep purple color within 10 minutes. 

Dimethyl-4-silacyclohexadienylidene (lv) is of interest as a potential source of silaxylene 24, however, all attempts to convert the carbene into an aromatic compound failed.107 The only isolated product from gas phase reactions is the dimer 25. In solution, carbene lv was found to add stereospecifically to cis-2-butene. With butadiene as trapping reagent both the products of the 1,2- and 1,4-addition 26 and 27, respectively, are observed (Scheme 21).107 In addition, silacyclopentene 28 is formed, which is the trapping product of cyclo-... 

The conversion of aromatic compounds comprises coupling, nuclear and ben-zylic substitution, and in some cases, addition. Homo- and in a more limited scope, heterocoupling is achieved for unsubstituted and substituted aromatic compounds in direct or indirect anodic processes. Chemically, there is a limited variety of expensive oxidation reagents available, but a large scope of transition... 

Under forcing conditions, Grignard reagents add to certain aromatic compounds. For example, the addition of PhMgBr to naphthalene takes place at 200 °C (Scheme 83) °. After treatment of the crude product with chloranil (for dehydrogenation), 1-phenylnaph-thalene is obtained in 34% yield. 

This mode of anodic addition involves oxidation of the substrate RH, an olefin or aromatic compound, to a radical cation, in contrast to the oxidations of the reagent Nu , depicted in the preceding sections a) and b). The adduct is formed in a EC ECj j- sequence (Eq. (119)) ... 

Nucleophilic Reactions of Aromatic Heterocyclic Bases Heterocyclic aromatic compounds containing a formal imine group (pyridine, quinoline, isoquinoline, and acridine) also react readily with nucleophilic reagents. A dihydro-derivative results, which is readily dehydrogenated to a new heteroaromatic system. Since the nucleophile always attacks the a-carbon atom, the reaction formally constitutes an addition to the C=N double bond. An actual localization of the C=N double bond in aromatic heterocyclic compounds is incompatible with molecular orbital theory. The attack of the nucleophilic reagent occurs at a site of low 77-electron density, which is not... 

The bromine solution is red the product that has the bromine atoms attached to carbon is colorless. Thus a reaction has taken place when there is a loss of color from the bromine solution and a colorless solution remains. Since alkanes have only single C—C bonds present, no reaction with bromine is observed the red color of the reagent would persist when added. Aromatic compounds resist addition reactions because of their aromaticity the possession of a closed loop (sextet) of electrons. These compounds react with bromine in the presence of a catalyst such as iron filings or aluminum chloride. 

The electrophilic fluorine of AcOF was also used for aromatic fluorinations. Activated aromatic compounds produced mainly the ortho fluoro derivatives in yields of up to 85%267. The dominant ortho substitution was a result of the addition of AcOF across the most electron-rich region of the aromatic ring. A subsequent spontaneous elimination of AcOH restored the aromaticity, but in cases where this was not possible the resulting cyclohexa-diene reacted very rapidly with the reagent and tars were obtained. Only in certain cases and with careful monitoring could the corresponding adducts be isolated (equation 151.)... 

In the absence of LiC104, the acylations proceed only sluggishly. However, a homogenous solution is obtained and the start of the reaction is observed only after the addition of the above mentioned triflate to a suspension of LiC104, acetic anhydride and the aromatic compound. Thus, the highly reactive cationic acylation reagent is formed from acetic anhydride and LiC104 only after the addition of the triflate M(OTf)3 (M = Yb, Sc). 

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