Preparation from aromatic

Sulfur Tetrafluoride and Aromatic Carboxylic Acids. Ben2otrifluorides also are prepared from aromatic carboxyhc acids and their derivatives with sulfur tetrafluoride (SF (106,107). Hydrogen fluoride is frequently used as a catalyst. Two equivalents of sulfur tetrafluoride are required ... 

Polycarbonates. Polyarjiates are aromatic polyesters commonly prepared from aromatic dicarboxylic acids and diphenols. One of the most important polyarylates is polycarbonate, a polyester of carbonic acid. Polycarbonate composite is extensively used in the automotive industry because the resin is a tough, corrosion-resistant material. Polycarbonates (qv) can be prepared from aUphatic or aromatic materials by two routes reaction of a dihydroxy compound with phosgene accompanied by Hberation ofHCl(eq. 5) ... 

Not surprisingly a number of other poly(aryl ethers) have been prepared from aromatic dihalides not containing sulphone links. For example, a number have been prepared from difluorobenzophenone and, in general, it is found that such materials have TgS about 30-40°C lower than the corresponding sulphone polyether. In fact it is generally found that the higher Tg values are obtained with the sulphone polyethers. 

Nitroalkenes prepared from aromatic aldehydes are especially useful for natural product synthesis. For example, the products are directly converted into ketones via the Nef reaction (Section 6.1) or indoles (Section 10.2) via the reduction to phenylethylamines (Section 6.3.2). The application of these transformations are discussed later here, some examples are presented to emphasize their utility. Schemes 3.3 and 3.4 present a synthesis of 5,6-dihydroxyindole66 and asperidophytine indole alkaloid,67 respectively. 

Aromatic aldehydes (benzaldehyde and its derivatives) are prepared from aromatic hydrocarbons by the following methods ... 

Many heterocyclic polymers have been produced in an attempt to develop high-temperature-resistant polymers for aerospace applications. Among these are the polybenzimidazoles (PBIs), which are prepared from aromatic tetramines and esters of dicarboxylic acids (structure 4.63). In standardized procedures, the reactants are heated to below 300°C forming soluble prepolymer, which is converted to the final insoluble polymer by further heating ... 

Aromatic azo polymers have been prepared from aromatic diamines using cupric ions as catalyst for an oxygen-oxidation in pyridine or dimethylacet-amide-pyridine solution [82],... 

The polyamide membranes prepared from aromatic diamines and aliphatic dichlorides, or from aliphatic diamines and aromatic dichlorides may be feasible for ultrafiltration as well as aliphatic polyamide membranes. Ohya 57) investigated the separation characteristics of asymmetric poly(xylyleneadipamide) (72) membrane under severe conditions of high temperature and high (or low) pH. 

POMERANZ-FRITSCH REACTION. Formation of isoquinolines by the acid-catalyzed cyclization of benzalaminoacetals prepared from aromatic aldehydes and aminoacetal. 

The Stacker reaction has been employed on an industrial scale for the synthesis of racemic a-amino acids, and asymmetric variants are known. However, most of the reported catalytic asymmetric Stacker-type reactions are indirect and utilize preformed imines, usually prepared from aromatic aldehydes [24]. A review highlights the most important developments in this area [25]. Kobayashi and coworkers [26] discovered an efficient and highly enantioselective direct catalytic asymmetric Stacker reaction of aldehydes, amines, and hydrogen cyanide using a chiral zirconium catalyst prepared from 2 equivalents of Zr(Ot-Bu)4, 2 equivalents of (R)-6,6 -dibromo-1, l -bi-2-naphthol, (R)-6-Br-BINOL], 1 equivalent of (R)-3,3 -dibromo-l,l -bi-2-naphthol, [(R)-3-Br-BINOL, and 3 equivalents of N-methylimida-zole (Scheme 9.17). This protocol is effective for aromatic aldehydes as well as branched and unbranched aliphatic aldehydes. 

US 5,204,399 (American) 1991 Thermally conductive thermoplastic polyimide film die attach adhesives and their preparation National Starch and Chemical Investment Holding Corp. R Edelman Adhesive formulations having excellent die shear strength A polyimide-siloxane was prepared from aromatic amines, bis aminophe-noxybutylsiloxane and aromatic dianhydrides... 

Ni(0) obtained from electrochemical reduction of NiBr2 in THF/HMPA acts as an efficient catalyst for the electroreductive coupling of ethylene with aryl halides to give 1,1-diarylethanes 217 (equation 109). By proper control of reaction conditions, such as reduction potential, solvent and supporting electrolyte, it can be shown that substituted olefins can be prepared from aromatic halides and alkenes164. 

Because diaryl telluriums can be prepared from aromatic hydrocarbons and tellurium followed by reduction of the diaryl tellurium dichlorides, the overall reaction sequence converts arenes to biaryls. The formation of benzene from diphenyl tellurium and Raney nickel was also reported3. 

Arenediazonium chlorides react with elemental tellurium to form diaryl tellurium dichlorides in yields not exceeding 40%. The diazonium salts were prepared from aromatic amines and amyl nitrite14. 

The Hantzsch pyridine synthesis is an old discovery (1882) which sprang into prominence in the 1980s with the discovery that the dihydropyridine intermediates prepared from aromatic aldehydes are calcium channel blocking agents and therefore valuable drugs for heart disease with useful effects on angina and hypertension. 

These plastics, also known as pyrrones, are experimental materials prepared from aromatic dianhydrides and aromatic tetraamines. The polymer syntheses provide soluble prepolymers that are converted to the pyrrone structures by thermal or chemical dehydration. The precursors can be used to cast films or coatings, or can be molded under very high pressures into filled or unfilled forms. The pyrrones combine some of the best properties of the polybenzimidazoles and polyimides. The pyrrone films are exceptionally radiation resistant and retain their strength properties after 10,000 megarads of 1-MeV electrons. 

One-pot synthesis of ( )-alkenes has been directly performed from nitromethane by a radical process (Liu and Yao, 2001). In fact, the strategy is to react P-nitrostirene (3) as shown in Figure 2.1, in situ prepared from aromatic aldehydes (1) with nitromethane (2) in the acetic acid solution with a catalytic amount of ammonium acetate at 70-100°C, with triethylborane in the biphase of diethyl ether and aqueous solution in the presence of oxygen in air as radical initiator, to generate (4). 

Since volatile, anhydrous hydrogen fluoride is extremely corrosive and toxic, the fluorodediazo-niatron of aromatic amines with this agent require.s special apparatus and. safety conditions, which are not available in most laboratories. Thus, the decomposition of diazonium tclra-fliioro bo rates, which can be readily prepared from aromatic amines and casier-to-handle tetra-fluoroboric acid, is the commonest fluorodediazoniation process, usually referred to as the Balz-Schiemann reaction (see Vol. E 10a, p 705IT). 

Phenols can be prepared from aromatic hydrocarbons by sul-fonalion and hydrolysis of the resulting sulfonic acid. 

Aromatic nitriles generally cannot be prepared from the unreactive aryl halides (Sec. 25.5). Instead they are made from diazonium salts by a reaction we shall discuss later (Sec. 23.13). Diazonium salts are prepared from aromatic... 

Cyanophosphates can be prepared from aromatic or a,p-unsaturated aldehydes with diethvl nhnsnhn. rocyanidate (DEPC, (EtO)2P(0)CN) in THF using LiCN or LDA as a base. Deprotonation of a cyanophosphate with Bu Li in the presence of tetramethylethylenediamine in THF at --78 C followed... 

In the laboratory, simple phenols can be prepared from aromatic sulforae acids by melting with NaOH at high temperature (Section 16-2), Few functional groups can survive such harsh conditions, though, and the reaction is therefore limited to the preparation of alkyl-substituted phenols. Well see a better method of phenol preparation from aromatic amines in Section 24.8. 

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