Aromatic compounds from phenolic esters

There is also evidence that at least some of the phenolic aldehydes and dehydrodiferulic acid (Figure 1) are linked covalently to cell wall polysaccharides. When ryegrass cell walls were treated with cellulase, the aldehydes and the acid were released as water-soluble carbohydrate-aromatic compounds from which the aromatics were released by cold sodium hydroxide treatment (6,7). This suggests that these compounds are either ether-linked or, in the case of the acid, ester-linked to the polysaccharides. 

The Fries rearrangement used for the preparation of aryl ketones from phenolic esters is now one of the most significant reactions in the synthetic chemistry of aromatic compounds, both in the classical version (equation 99) and in the newest modifications (see Section IV.D.3). 

Molasses. A large number of volatile and nonvolatile compounds have been identified in the flavor fractions of various types of molasses (51-621. Compound classes identified include aliphatic and aromatic acids, aldehydes, phenols, lactones, amines, esters, furans, pyrazines, and sulfides. Most of these compounds can arise from carbohydrate degradation through a number of traditional pathways especially because residual nitrogen-containing sources are present. 

The synthesis of bistannylated aromatic compounds can be achieved in good yields via a simple two-step sequence from phenols [44]. This methodology enables, for example, the transformation of BINOL into the corresponding aryl diethylpho-sphate ester, which by reaction with Me3Sn ions in liquid ammonia under irradiation affords 2,2 -bis(trimethylstannyl)-l,l -binaphthyl in an overall yield of 66% (Scheme 10.27). 

Aromatic amines, like phenols, are very easily nitrated. However, primary and secondary amines in particular readily undergo oxidative side reactions, so that it is advisable to protect the amino group by acylation or by conversion by an aldehyde into the Schiff base. Even using a large excess of sulfuric acid protects the amino group to a considerable extent, owing to formation of the ammonium salt, but then entry of the nitro group is directed to a considerable extent into the meta-position. The usual A-acyl derivative is the acetyl compound, but benzoyl, /7-toluenesulfonyl, oxalyl, ethoxycarbonyl (from chloro-formic ester), and phthaloyl derivatives are also used. 

Typical analyses include the detection and determination of paraffins, aromatics, olefins, acetylenes, aldehydes, ketones, carboxylic acids, phenols, esters, ethers, amines, sulfur compounds, halides, and so on. From the IR spectrum, it is possible to distinguish one polymer from another or determine the composition of mixed polymers or identify the solvents in paints. Atmospheric pollutants can be identified while still in the atmosphere. Another interesting application is the examination of old paintings and artifacts. It is possible to identify the varnish used on the painting and the textile comprising the canvas, as well as the pigments in the paint. From this information. 

Lichens had to evolve diverse biosynthetic pathways to produce such complex arrays of secondary metabolites polyketide, shikimic acid, and mevalonic acid pathways. Most of the lichen substances are phenolic compounds. Polyketide-derived aromatic compounds, depsides, depsidones, dibenzofurans, xanthones, and naphthoquinones, are of great interest. Compounds from other pathways are esters, terpenes, steroids, terphenylquinones, and pulvinic acid (Fahselt 1994 Cohen and Towers 1995 Muller 2001 Brunauer et al. 2006, 2007 Stocker-Worgotter and Elix 2002 Johnson et al. 2011 Manojlovic et al. 2012). So, many lichens and lichen products have proved to be a source of important secondary metabolites for food and pharmaceutical industries (Huneck 1999 Oksanen 2006)... 

Apart from cinnamoyl esters, aromatic amino acids (see Chap. 5.1) and the alcohols corresponding to the common hydroxycinnamic acids, as well as some glycerolaryl compounds, are of interest in connection with the biosynthesis of lignin and other polycyclic phenolic compounds. 

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