Hydroxy cinnamaldehyde

Quinone methides play an important role in lignification. They are produced directly, as intermediates, when lignin monomers, be they hydroxycinnamyl alcohols, hydroxy-cinnamaldehydes, or hydroxycinnamates, couple or cross-couple at their 8- positions. A variety of postcoupling quinone methide rearomatization reactions leads to an array of structures in the complex lignin polymer (Fig. 12.2). 

Hydroxy-benzaldehyde (phenolic aldehyde) 2-Hydroxy-cinnamaldehyde (phenolic)... 

H. Stark and co-workers prepared novel histamine Hs-receptor antagonists with carbonyl-substituted 4-[(3-phenoxy)propyl]-1/-/-imidazole structures. The Meyer-Schuster rearrangement was used for the synthesis of one of the compounds. The p-hydroxybenzaldehyde derivative was reacted with ethynylmagnesium bromide to afford a secondary propargylic alcohol. Upon hydrolysis with 2N HCI in a refluxing ethanol/acetone mixture, the corresponding p-hydroxy cinnamaldehyde was obtained. 

Monotetpene, linalool, limonene, a-pinene, dtronellal, dtral, geranial Pyruvic acid, acetaldehyde, ethanol Isopropanal, isopropanol, a-keto-isobutyric add 3-Methylbutanal, 3-methylbutanol, a-keto-isocaproic add 2-Methylbutanal, 2-methylbutanol Benzaldehyde, phenylacetaldehyde, dnnamaldehyde Hydrocinnamaldehyde, p-hydroxybenzaldehyde p-Hydroxy phenylacetaldehyde, p-hydroxy dnnamaldehyde, p-hydroxy cinnamaldehyde... 

It is possible to replace the vanillin in the reagent by 4-dimethylaminobenzaldehyde, 4-hydroxybenzaldehyde, salicylaldehyde, /w-anisaldehyde, cinnamaldehyde, 4-hydroxy-benzoic acid or vanillic acid [3]. However, the range of colors obtained is not so broad. 

CINNAMIC ACID, CINNAMALDEHYDE AND CINNAMYLALCOHOL] (Vol 6) (S)-9-(3-Hydroxy-2-phosphonylmethoxypropyl)ademne... 

With benzaldehyde 144 or halogenated derivatives (Cl, F) as acceptors the yeast-PDC-catalyzed addition proceeds with almost complete stereoselectivity to furnish the corresponding (R)-configurated 1-hydroxy-1-phenylpropanones 145 [447]. For practical reasons, whole yeast cells are most often used as the catalyst, with only small loss of enantioselectivity [423,424]. The conversion of benzaldehyde in particular has gained industrial importance because the acyloin is an important precursor for the synthesis of L-(-)-ephedrine [448]. Otherwise, the substrate tolerance is remarkably broad for aromatic aldehydes on the laboratory scale, however, yields of acyloins are usually low because of the prior or consequent reductive metabolism of aldehyde substrate and product, giving rise to considerable quantities of alcohol 146 and vicinol diols 147, respectively [423,424,449], The range of structural variability covers both higher a-oxo-acids (e.g. -butyrate, -valerate) as the donor component, as well as a,/J-un-saturated aldehydes (e.g. cinnamaldehyde 148) as the acceptor [450]. 

Benzalacetone Methyl vinyl ketone A -Cholestenone Cinnamaldehyde Dimethyl maleate 5-Hydroxy-2-hexenoic acid -lactone... 

C. (E)-2-(4-Hydroxy-6-phenyl-5-hexenyl)-1H-lsolndole-1,3(2H)-dione 4. The THF solution of the copper-zinc reagent is cooled to -78°C and 19.9 mL (162 mmol) of boron trifluoride etherate (Note 13) is added dropwise. The reaction mixture is warmed to -30 C and stirred for 30 min, then cooled to -60°C. (E)-Cinnamaldehyde (5.71 g, 43.2 mmol) is added slowly via a syringe. The reaction mixture is allowed to stir at -30 C for 14 hr (Note 14) and for 30 min at 0°C. After this time, conversion is complete as Indicated by GLC analysis and the reaction mixture is poured into an Erlenmeyer flask containing 500 mL of ethyl acetate, 100 mL of a saturated aqueous... 

Cinnamaldehyde is converted by H2O2 under basic conditions into the 3-hydroxy-1,2-dioxolane... 

Dakin and Dakin-like Reactions Cinnamaldehydes or aromatic structures containing carbonyl substituents para to a free phenolic hydroxyl group (e.g., p-hydroxy-acetophenones) react with stabilized alkaline peroxide to form benzaldehydes and hydroquinones, respectively [37,38], Structures containing aryl-a-carbonyl substituents para to an etherilied phenolic group are degraded more slowly [39]. 

The a-P double bond in hydroxy- or methoxy-substituted stilbenes should also be stable to hydroperoxide ion. It is the electron withdrawing carbonyl group in cinnamaldehydes that makes their double bond susceptible to nucleophilic attack. 

The efficiency of a Raney nickel catalyst for hydrogenation of carbonyl groups is much diminished if the catalyst is treated with 0.1% acetic acid or an amino acid, particularly dibasic amino acids or L-phenylalanine but the efficiency for hydrogenation of C=C double bonds remains unaffected. Thus mesityl oxide was hydrogenated to isobutyl methyl ketone selectively and in good yield but cinnamaldehyde could not be reduced in this way.161 For asymmetric hydrogenation with Raney nickel modified by optically active 2-hydroxy carboxylic acids see Tatsumi et al.162... 

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