Benzene ring functionalization

Benzene Ring Functionalization Hartwig Synthesis of Taiwaniaquinol B... 

Regioselective lithiations have also been utilized to prepare other benzene-ring functionalized indoles. For example, the selective halogen-metal exchange of 4,7-dibromoindole 152 led to the formation of 7-lithioindole intermediate 153, which in turn gave indole-7-carboxaldehyde 154 upon treatment with DMF <03TL5987>. 

As shown in reaction (6.28), the formation of m/z 92 is a diagnostic reaction of alkyl benzenes that have at least three carbon atoms in the alkyl chain (see Figure 6.4). In this example of the McLafferty rearrangement, the benzene ring functions as an efficient y-hydrogen acceptor. 

The sensitivity of infrared absorption spectroscopy toward subtle changes in crystal structure has led to its widespread use in the investigations of pharmaceutical compounds that exhibit polymorphism. For example, three concomitant polymorphs of l,3-bis(w-nitro-phenyl)urea had been reported in 1899 as yellow prisms, white needles, and yellow tabular crystals, and FT IR spectroscopy was used during a more detailed investigation of the system. In this work, complete assignments for the absorption bands associated with hydroxyl, amide, nitro, and benzene-ring functional groups were developed in order to obtain a deeper... 

In an analogous way, soluble substituted poly(p-phenylene)s were prepared from substituted benzene rings functionalized with MgCl and Br in para position (see Formula 16.10). It proved to be necessary to add LiCl in addition to the Ni-catalyst to achieve low DPs (1.17-1.27) and Mns up to 36 kDa [130]. Furthermore, it was feasible to synthesize diblock copolymers, when the poly(p-phenylene) was prepared first and used as a macroinitiator for thiophene monomers. The same approach also allowed to perform CCPs of 2,5-dihalo N-hexylpyrrol, but again... 

Many aromatic aldehydes (having the -CHO group joined directly to the benzene ring) undergo polymerisation when heated with a solution of potassium cyanide in aqueous ethanol. Thus benzaldehyde gives benzoin, a compound of double function, since it contains both a secondary alcoholic and a ketonic... 

Laurino examined a similar method in which methanesulfonanilides were alkylated with bromoacetaldehyde diethyl acetal and then cyclized with TiCU[4J. 1 hese methods presumably involve generation of an electrophilic intermediate from the acetal functionality, followed by an intramolecular Friedel-Crafts reaction. As a consequence, the cyclization is favoured by ER substituents and retarded by EW groups on the benzene ring. 

The high degree of crystallization and the thermal stability of the bond between the benzene ring and sulfur are the two properties responsible for the polymer s high melting point, thermal stability, inherent flame retardance, and good chemical resistance. There are no known solvents of poIy(phenyIene sulfide) that can function below 205°C. 

Since, in fhe excifed sfafe, fhe fluorine atoms may be above or below fhe plane of fhe benzene ring fhe potential function for Vu is W-shaped, like fhaf in Figure 6.4f(b). Fitting the observed vibrational energy levels to the potential function in Equation (6.93) gives fhe heighf of fhe barrier to planarify as 78 cm. ... 

The chemical properties and reactions of the aminophenols and their derivatives are to be found in detail in many standard chemical texts (25). The acidity of the hydroxyl function is depressed by the presence of an amino group on the benzene ring this phenomenon is most pronounced with 4-aminophenol. 

A number of aromatic amines also function as cross-linking agents. By incorporating the rigid benzene ring structure into the cross-linked network, products are obtained with significantly higher heat distortion temperatures than are obtainable with the aliphatic amines. 

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