Diaryls dihydroxy

Transesterification has become a convenient method for synthesi2ing high alkyl, aryl, or alkyl aryl carbonates. Fiber- and film-forming polycarbonates are produced by transesterifying dialkyl, dicycloalkyl, or diaryl carbonates with alkyl, cycloalkyl, or aryl dihydroxy compounds (62). 

Dioxo-l,3-diaryl-propane dimerisieren reduktiv zu 3,4-Dihydroxy-1,6-dioxo-1,3,4.6-tetra-aryl-hexanen I, 1,3,5,6-Tctraaryl-2,4,7-trioxa-tricyclo[3.2.1.13 6]n0nanen II und 1,2,4-Trihydroxy-l,2,4-triaryl-3-aroyl-cyclopentancn III4 ... 

The final products of oxidation of diarylselenides and tellurides (and sulfides as well) in the presence of nucleophiles are the corresponding chalcogen (IV) compounds. In the presence of water, the selenoxide or telluroxide (or the corresponding dihydroxy selenane or tellurane) is the final product. This still leaves several possible pathways, leveraged from early mechanistic studies done using electrochemical techniques on diaryl sulfides and outlined by Engman (Fig. 32). In these pathways, the initial radical cation can react with a nucleophile present in solution, or the dication resulting from further oxidation or disproportionation can do so. 

Mit praparativ interessanten Ausbeuten erfolgt auch die Umlagerung der 3,4-Dihydroxy- 1,2,5,6-tetraalkyl-l,5-hexadiene20-22. Je nach Reaktionsbedingungen werden dabei Derivate des 2-Vinyl-2-butenals bzw. 2-Vinyl-3-butenals erhalten (s. Tab. 110, S. 544). Ebenso fiihren 1,6-Dialkyl- bzw. -Diaryl-3,4-dihydroxy-1,5-hexadiene vorzugsweise zu Aldehyden23. 

Azobenzene, 2-hydroxy-5-methyl-2 -carboxymethyleneoxy-metal complexes dyes, 75 Azo compounds o-amino-o -hydroxydiaryl transition metal complexes, 57 o,o -diaminodiaryl cobalt complexes, 58,60 o, o -dihydroxy diaryl copper complexes, 55,57 p/Ca,47... 

A variation on the aromatic nucleophlic displacement chemistry described above employs the cuprous chloride catalyzed polycondensation of an aromatic dihydroxy compound with a divalent aromatic dibromo diaryl compound. This method has the advantage that the dibromo diaryl compound does not have to be activated by the sulfone group. This route can therefore be employed for copolymers and ter-polymers that incorporate the sulfone moiety along with other non-sulfone-containing repeat units. This synthesis route is commonly known as the Ullmann sjmthesis [4]. 

Dicarbonyl Compounds.— 2,3-Dihydroxy-l,4-dioxan functions as a stable synthetic equivalent to glyoxal, particularly in the synthesis of a variety of heterocycles. The dioxan overcomes the prerequisite preparation of pure glyoxal immediately prior to its use (because of its tendency to polymerize) and offers an alternative available for reaction under non-aqueous conditions. Monoprotected a-keto-aldehydes are seldom available by selective derivatization of the parent dicarbonyl compound. However, 1,1,2,2-tetramethoxy-alkanes, readily prepared from a,a-dichloro-aldehydes, undergo regioselective hydrolysis to give l,l-dimethoxyalkan-2-ones. The sequence from the dichloro-aldehyde may be carried out without isolation of the tetramethoxylated intermediate. a,a-Bis(phenylseleneno)-aldehydes may be prepared from aldehydes or the intermediate a-(phenylseleno)-aldehyde by treatment with morpholinophenyl-selenenamide. a-(Arylseleno)-ap-unsaturated aldehydes result from the electrochemical oxidation of 3-hydroxyalkynes in the presence of a diaryl diselenide [equation (42)]. Treatment of a,a -dibromo-ketones with primary... 

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