Oxidative condensation, benzene derivatives

The benzene derivatives containing the fluorinated sulfone have been prepared either by nucleophilic substitution of the 4-fluorophenyl derivative (e.g. 1) or by starting with the appropriately substituted sodium thiophenoxide and reacting with perfluoroalkyl iodide follow by oxidation with either MCPBA or chromium oxide (12. li.) The biphenyl derivatives have been prepared by palladium catalyzed cross coupling chemistry of the 4-bromophenyl derivative (e.g. 2) with substituted phenyl boronic acid (yields 37-84%) (JLH, .). Compound 16 has been prepared by palladium catalyzed cross coupling of (4-bromophenyl)perfluorohexyl sulfone with vinyl anisole in 37 % yield (JJL). The vinyl sulfones, 7 and 9, have been prepared by condensation of CH3S02Rf (JJL) with the appropriate aldehyde (yields 70,and 73%) following a literature procedure (1 ). Yields were not optimized. 

The rates of formation of some phenazines by cyclization of di- and monoimines of JV-(2-aminophenyl)-l,4-benzoquinone have been determined spectrophotometrically. The reaction of 2-aminoindamines (quinoneimines) is a similar example (see Hotiben-Weyl, Vol. 7/3 b, p 330). The oxidation of benzene-1,2,4-lriamine (16) takes place through a series of intermediates, c.g. initial oxidation of 2-amino-l, 4-quinonediiminc (17) is followed by its condensation with beiizene-1,2,4-triamine (16) which leads to the formation of the indamine derivative 18 which, on further oxidation, undergoes cyclization to the amino-substituted phenazine. Different isomers of phenazinetriamines 19 can thus be formed. 

A comprehensive review (260 refs.) on the synthesis of carbohydrates from noncarbohydrate sources covers the use of benzene-derived diols and products of Sharpless asymmetric oxidation as starting materials, Dodoni s thiazole and Vogel s naked sugar approaches, as well as the application of enzyme-catalysed aldol condensations. The preparation of monosaccharides by enzyme-catalysed aldol condensations is also discussed in a review on recent advances in the chemoenzymic synthesis of carbohydrates and carbohydrate mimetics, in parts of reviews on the formation of carbon-carbon bonds by enzymic asymmetric synthesis and on carbohydrate-mediated biochemical recognition processes as potential targets for drug development, as well as in connection with the introduction of three Aldol Reaction Kits that provide dihydroxyacetone phosphate-dependent aldolases (27 refs.). A further review deals with the synthesis of carbohydrates by application of the nitrile oxide 1,3-dipolar cycloaddition (13 refs.). ... 

Products from the pyrolysis of cellulose in the absence of a catalyst were found to be mainly derivatives of 1,6-anhydro-D-glucoseand other, unsaturated, products. One product, formed in 1.4% yield, was found to be 1,5-anhydro-4-deoxy-D- /yc ro-hex-l-en-3-ulose. This product was also formed during the pyrolysis of amylose, amylopectin, and laminarin. A further product from cellulose, probably formed as an oxidation product, was 3,5-dihydroxy-2-methyl-4/f-pyran-4-one. Sixty-three compounds were detected in the condensate of smoke produced by pyrolysis of cellulose. These compounds included furans, cyclic ketones, lactones, benzene derivatives, aliphatic ketones, and aldehydes. One of the major products was 2-hydroxy-3-methyl-cyclopenten-l-one. 

Fig. 6. Key intermediates derived from benzene. The alkylation reaction shown employs ethylene oxide. Hydrazine condenses with acetoacetic acid to form...

Benzocyclobutene-l,2-dione (11) can be condensed with benzene-1.2-diamine to provide an annulated quinoxaline (cf. Houben-Weyl, Vol. E9b/Part 2, p203), which on oxidation with hydrogen peroxide in acetic acid leads to the 1,4-diazocine derivative 12.34... 

A mixture of the diol (2 mmol) and dibutyltin oxide (545 mg 2.2 mmol) in benzene was refluxed overnight with azeotropic removal of water by a Dean-Stark condenser Evaporation of (he solvent at 100 0 then gave the crude stannylene derivative, which was used without further purification. Btominoiyses were carried out either on solutions of the stauaykne derivatives in benzene (5 mL) in the presence of 4-A molecular sieves (2 g)... 

The aldehydes 346 and 347 were prepared from the methoxyl derivatives by osmic acid sodium chlorate oxidation and deketalization followed by base-catalyzed condensation in an overall yield of 50%. Acetalization of 346 with /i-toluenesulfonic acid and ethylene glycol in refluxing benzene afforded the acetal 348. The latter has an active site at C-6 suitable for the introduction of oxygen substituents at this position. 

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