Chloranil aldehydes

In 1956, Braude et al.92 showed that treatment of allylic, benzylic and propargylic alcohols with o-chloranil (tetrachloro-l,2-benzoquinone) (82) provided the corresponding aldehydes and ketones. Under the mild conditions employed, involving room temperature or refluxing ether, saturated alcohols remained unaffected. 

Under oxidative conditions, both alkyl and aryl aldehydes condense, giving the 2-alkyl- or 2-aryladenine derivatives.Oxidation of the dihydro intermediate, which is not isolated, is effected either atmospherically, with oxygen and palladium in methanol, or by treatment with tetrachloro-l,4-benzoquinone (chloranil) in dimethylformamide, e.g. formation of 3. ... 

A general synthesis of quinazoline 1,3-dioxides and their 1,2-dihydro derivatives was devised by Taylor and Bartulin. In this synthesis o-hydroxyl-aminobenzaldehyde oxime condensed with aldehydes and ketones to yield 2,2-disubstituted 1,2-dihydro-l-hydroxyquinazoline 3-oxides (63). When the dihydro compounds (63 R1 = H) derived from aldehydes or from formaldehyde were oxidized with chloranil, benzoquinone, or mercuric oxide, 2-substituted quinazoline 1,3-dioxides (64) and the parent quinazoline 1,3-dioxide (63 R = H) were produced.173... 

As shown in Scheme 1, the synthesis of fert-butyl phenalenyl radical 10 started from 2,7-di-ferf-butylnaphthalene in ten steps. Bromination of 2,1-di-tert-butylnaphthalene gave 6 in high yield, which was converted into aldehyde by lithiation followed by reaction with DMF. Successive Reformatsky reaction afforded ester 7, which upon reduction, hydrolysis, and Friedel-Crafts acylation reaction gave the phenalanone 8. The key intermediate 9 was then obtained as pale yellow crystals by reduction of 8 and subsequent dehydration. Oxidation of 9 with p-chloranil in degassed toluene led to a blue neutral radical solution while similar treatment in hexane gave deep blue needles. This crystal showed high stability in the absence of air, while changing into phenalanone derivatives and other byproducts in 1 week in air. 

A more straightforward method to mew-monosubstituted, [)-unsubstituted porphyrins has been reported by Senge and co-workers in 2002 [54] and consists in the condensation of various type of aldehydes with dipyrromethane and pyrrole-2-carbaldehyde leading to dilferently substituted mew-monosubstituted porphyrins with moderate yields (2-12 %). A similar method was used to prepare (SBF)PH2 (Scheme 6) [52]. In a typical experimental procedure, dipyrromethane 2, pyrrole-2-carbaldehyde 4 and aldehyde 1 dissolved in freshly distilled dichlo-romethane were stirred with trifiuoroacetic acid, under an argon atmosphere, for 16 h. After addition of chloranil, triethylamine was added and the solvent was... 

A novel type of photoproduct was observed for ortfio-chloranil (18). Whereas various aldehydes studied gave the expected monoesters (98) in moderate to good yields, iso- and 2-ethylbutyraldehyde afforded the tetrachloro-3,3-dialkyl-2,3-dihydro-benzo[l,4]-dioxin-2-ols99 (Scheme 29). The formation of these unusual products was explained by initial abstraction of the tertiary methine hydrogen in preference to the formyl hydrogen, followed by rapid transformation into the 1,4-adduct 99. 

Porphyrin Synthesis. Afeso-tetraalkylporphyrins are formed in good yields ftom condensation of aliphatic aldehydes with pyrrole thermally activated KIO catalyzes the polymerization-cyclization to porphyrinogen, followed by p-Chloranil oxidation (eq 11). ... 

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