2-Hydroxy-4-methoxy acetophenone

QUINACETOPHENONE MONOMETHYL ETHER (Acetophenone, 2-hydroxy-5-methoxy-)... 

Silyl enol ethers are quite reactive towards IOB-boron trifluoride (or tetrafluoroboric acid) and can be considered as valuable starting materials for several reactions of synthetic importance. Of special interest is their use for carbon-carbon bond formation 1,4-diketones and unsaturated ketones are the products of such reactions further, they can be transformed to oc-hydroxy, methoxy or trifyloxy ketones. With tetrafluoroboric acid IOB forms a yellow solution containing the highly electrophilic Phi+ OH BF4 , stable up to 0°C. This species reacts readily with silyl ethers of several ketones, notably acetophenones, at —78°C, forming an unstable iodonium ion (ArCOCH2I+ Ph) which with another silyl ether affords 1,4-diketones. 

Acetophenone, 4 -hydroxy- Acetophenone, p-hydroxy-. See p-Hydroxyacetophenone Acetophenone, 4 -isopropyl-. See p-Isopropylacetophenone Acetophenone, 2-methoxy-2-phenyl-. See Benzoin methyl ether... 

Cassimjee et al. reported [22] that a variant engineered aminotransferase at TrpOOCys from Chromohacterium violaceum showed a 29-fold increase on spedfidty for synthesis of (S)-phenylethylamine and about fivefold on spedfidty for 4 -substituted acetophenones, where the groups at 4 position were bromo, chloro, hydroxy, methoxy, nitro, methyl, and cyano. The amine donor was isopropylamine. The reaction schemes are shown in Figure 7.5. 

Mit Natrium-bis-[2-methoxy-athoxy]-dihydrido-aluminat konnen in sieden-dem Xylol Hydroxy-benzaldehyde und -acetophenone innerhalb weniger Stunden zu Al-kyl-phenolen reduziert werden (Vorschrift S. 171) z.B.2 ... 

Of interest is a comparison of a-methoxy with a-hydroxy substituents. The a-hydroxy carbenium ions correspond to protonated ketones and their pAR values may be derived from a combination of a hydration equilibrium constant and a pfor protonation of the ketone, as illustrated by the thermodynamic cycle based on acetophenone in Scheme 15.I37,I3X Corresponding data are available for benzaldehyde138,139 and acetone70,140,141 and lead to the values of... 

Comparisons of structurally related hydroxy- and methoxy-substituted cations show that hydroxy is more stabilizing by between 4 and 5 log units. This difference was recognized 20 years ago by Toullec who compared pifas for protonation of the enol of acetophenone and its methyl ether145 (-4.6 and 1.3, respectively) based on a cycle similar to that of Scheme 15, but with the enol replacing the hydrate, and a further cycle relating the enol ether to a corresponding dimethyl acetal and methoxycarbocation.146 Toullec concluded, understandably but incorrectly, that there was an error in the pA a of the ketone (over which there had been controversy at the time).147,148 In a related study, Amyes and Jencks noted a difference of 105-fold in reactivity in the nucleophilic reaction with water of protonated and O-methylated acetone and concluded that the protonated acetone lacked a full covalent bond to... 

Methyl 4-0-(4-methoxybenzyl)2,3-di-0-methyl-oc-D-glucopyranoside has been prepared [371] by Liptak s procedure (see Sect. 2.6). This lithium aluminium hydride — aluminium trichloride method was also used in the synthesis of 4-hydroxy-3-methoxy-benzyl [372], 4-hydroxy-3,5-dimethoxybenzyl [372], and 1-phenylethyl [373] ethers from the 4,6-acetals derived from vanillin, syringealdehyde, and acetophenone. Various vinylbenzyl ethers were prepared by the reaction of carbohydrates with vinylbenzyl chloride, and copolymerized with styrene [374]. 

A Castellan, N Colombo, C Cucuphat, and P Fomier, de Violet, Photo-degradation of Lignin A Photochemical Study of a Phenolic a-Carbonyl P-O-4 Lignin Model Dimer 4-Hydroxy-3-Methoxy-a-(2 -Methoxyphenoxy)-Acetophenone. Holzforschung 43 179-185, 1989. 

Low concentrations of ethyl-2-and 3-mercapto-propionate, mentioned earlier in this chapter, have a fruity aroma, whereas in larger quantities they have sulfurous smells. Acree et al. (1990) also demonstrated the presence of 2-amino-acetophenone in Vitis labrusca, as well as two furanones (4-hydroxy-2,5-dimethyl-3-furanone, commonly known as furaneol, and 4-methoxy-2,5-dimethyl-3-furanone) reminiscent of strawberries (Rapp et al., 1980). Most of these compounds have also been identified in Vitis vinifera wines, but at lower concentrations (Guedes de Pinho, 1994 Moio and Etievant 1995). 

Knoevenagel condensation under focused MWI for 1-7 min of 2-hydroxy or 2-methoxy-substituted benzaldehydes or acetophenones 99 and Meldrum s acid (100) using a solid catalyst combination of natural kaolinitic clay or Envirocats (EPZG, EPZIO) gave 3-carboxycoumarins 101 in 55-97% yields (Scheme 20) (99MI4). 

The rearrangement is found to be of intramolecular nature. The radical pair remains in the solvent cage and their recombination in the cage affords the acyl migration products, while hydrogen abstraction by the phenoxy radical from the solvent leads to the formation of phenol as by-product. When the reaction of phenyl acetate was carried out with deuterated phenol in methanol, the major products were ortho- and para-hydroxy acetophenones and phenol. Only trace amounts of crossover products were obtained [42]. The presence of methoxy substiment at meta- and para-positions increases the yield of ortho-Vries product [43]. For example, 39 gives 40. 

Preparation by chlorination of 2-hydroxy-5-methoxy-acetophenone with N-chlorosuccinimide in acetic acid containing magnesium acetate at r.t. for 24 h under nidogen atmosphere (80%) [2559,2560],... 

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