4-Hydroxyacetophenone

The addition of a little barium hydroxide to 2-hydroxyacetophenone and benzaldehyde in 96% ethanol followed by refluxing of the reaction mixture during 4 hours afforded the chalcone (benzylidene 2-hydroxyacetophenone) in 89% yield without the need for protection of the phenolic hydroxyl group and unaccompanied by impurities (reT74). 

The 2-hydroxyacetophenone derivative depicted, formed spontaneously from a tetraketone precursor in the presence of silica, itself derived in turn by ozonolysis of 3,6-dihydroindan-1-one acetal, has been regiospecifically recyclised with potassium hydroxide to 1,8-dihydroxy-3-methylnaphthalene (ref.75). 

Etherification of 4-hydroxyacetophenone in dimethyl sulphoxide containing potassium carbonate by the slow addition of methyl (S)-2-chloropropionate over 30 mins, and reaction with stirring during 6 hours at ambient temperature (with introduction of more potassium carbonate over a further 5 hours) gave methyl (R)-2-(4-acetylphenoxy)propionate (enantiomeric excess, 86%). 

Racemisation was suppressed by effecting the reaction at less than 50°C (ref.76). 

4-Hydroxyacetophenone in dichloromethane suspension after the addition of 1 mole proportion of diisopropylamine at -78°C during 20 mins, was then treated dropwise during 10 mins, with 1 mole of fluorosulphonic anhydride and following reaction for 30 mins, succeeded by aqueous work-up, 4-acetylphenyl fluorosulphonate was obtained in 95% yield (ref.77). 

Since two quaternary atoms and four CH atoms appear in the C NMR spectrum, the latter with a benzenoid coupling constant of 7-9 Hz, this is a disubstituted benzene ring, and the C signal with 5c = 162.2 fits a phenoxy C atom. The keto carbonyl (5c = 204.9) and methyl (5c = 26.6) resonances therefore point to an acetyl group as the only meaningful second substituent. Accordingly, it must be either o- or m-hydroxyacetophenone A or B the para isomer would show only four benzenoid C signals because of the molecular symmetry. 

Signal assignment is then no problem the C atoms whieh are bonded to the nitro groups C-2,6 and C-4 are elearly distinguishable in the C NMR speetrum by the intensities of their signals. 

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The treatment of 2-hydroxyacetophenone with hydroxylamine-O-sulfonic acid in dilute aqueous base produced 3-methyl-1,2-benzisoxazole. The mechanism was reported to be a C(2)—C(3) ring closure via intermediate (560) (Scheme 171). Salicylaldehyde failed to cyclize with dilute base, but with 20% KOH and hydroxylamine-O-sulfonic acid the transformation to 1,2-benzisoxazole succeeded (76MI41600). Kemp and Woodward isolated an oxime sulfonate (561) from salicylaldehyde and hydroxylamine-O-sulfonic acid and the subsequent decomposition gave 1,2-benzisoxazole in 95% yield (65T3019). 

Partial hydrolysis of a potentially heptadentate Schiff-base tripodal ligand derived from tris-(2-aminoethyl)amine and 2-hydroxyacetophenone, induced by copper(II) salts, was reported and the final copper(II) complex (377) was characterized.333 Using salicylaldehyde as a co-ligand, with a copper(II) complex (378), catalytic epoxidation was demonstrated 334... 

Investigation of Chlorine Substitution Effects in the Claisen-Schmidt Condensation of 2 -Hydroxyacetophenone with Chlorobenzaldehydes Over MgO... 

The Claisen-Schmidt condensation of 2 -hydroxyacetophenone and different chlorinated benzaldehydes over MgO has been investigated through kinetic and FTIR spectroscopic studies. The results indicate that the position of the chlorine atom on the aromatic ring of the benzaldehyde substantially affects the rate of this reaction. In particular, the rate increases in the following order p-chlorobenzaldehyde < m-chlorobenzaldehyde < o-chlorobenzaldehyde. The difference between the meta and para-substituted benzaldehyde can be attributed to electronic effects due to the difference in the Hammett constants for these two positions. Steric effects were found to be responsible for the higher rate observed with the o-chlorobenzaldehyde. 

Figure 1 Normalized 2 -hydroxyacetophenone concentration versus time data obtained during the reaction of 2-hydroxyacetophenone with different chlorobenzaldehydes over MgO para-chlorobenzaldehyde, meta-chlorobenzaldehyde, ortho-chlorobenzaldehydes and 2,3-...

The use of mesitoic acid esters has again been successfully employed by Burrows and Topping (1975) in the elucidation of intramolecular carbon acid participation. Under basic aqueous conditions, 2-acetylphenyl mesitoate [41] hydrolyses to yield mesitoic acid and 2-hydroxyacetophenone, reacting with intramolecular catalysis via the monoanion of the ketonic hydrate (see p. 192). However, in 47.5% aqueous ethanol containing potassium hydroxide, the reaction products from l-acetyl-2-naphthyl mesitoate [45] were found... 

Reaction of 2-hydroxyacetophenones in the Hurd-Mori reaction led to a range of 4-(o-hydroxyaryl)-l,2,3-thiadia-zoles 56. Subsequent treatment of these derivatives with base and an alkyl halide led to the formation of 2-benzofuransulfanyl derivatives 57 (Scheme 6) <2000T3933>. 

Method A The 2-hydroxyacetophenone (3 mmol) and acyl chloride (3.6 mmol) in PhH (20 ml) are stirred at 80°C with aqueous K,CO, (I0%, 20 ml) and TBA-HS04 (0.5 g, 1.5 mmol) for 2-3 h until the ester is completely formed. The PhH phase is separated, washed with H.O (3 x 20 ml) and dried by azeotropic distillation. Ring closure is effected by the addition of TosOH (1.55 g, 9 mmol) in PhH (20 ml) and azeotropic distillation. The organic solution is washed with aqueous NaHCO, (10%, 50 ml) and evaporated to yield the chromone. 

Method B The acyl chloride (12 mmol) in CH2C12 (10 ml) is added dropwise over 15 min to the 2-hydroxyacetophenone (10 mmol), TBA-HS04 (0.1 g, 0.3 mmol) and aqueous K,CO, (20%, 30 ml) at room temperature. The mixture is stirred for ca. 7 h and the organic phase is then separated, washed well with H20 and brine, dried (MgS04), and evaporated to yield the chromone (70-95%). 

Method A Following procedure 6.3.19, the crude aldol condensation product from 2-hydroxyacetophenone (5 mmol) and (PhCH=CHCO)20 (1.63 g, 5 mmol) is taken up in CH2C12 (10 ml) and heated under reflux with TosOH (1 g) for 30 min. Water is added and the precipitated flavone (-75%) is collected. 

Chlorobenzene. 4-Chlorophenol. 4-Nitroaniline. 4-Nitrophenol. Parathion. Phenol Hydroxyacenaphthenone. see Acenaphthene Hydroxyacetaldehyde. see 2-Methvl-2-butene. 1.1.2-Tricliloroethane. Vinyl chloride 2-Hydroxyacetanilide. see Aniline Hydroxyacetone, see 2-Methvl-2-butene 2 -Hydroxyacetophenone, see Naphthalene... 

In addition to the absorptions attributable to aryloxy radicals. Fig. 1 displays a broad shoulder around 315 nm, much longer-lived, which is assigned to a 2,4-cyclohexadienone. This intermediate decays with a rate of 1.25 0.1 sec in hexane solution, to give 2-hydroxyacetophenone (11) via 1,3-hydrogen shift. The rate of appearance of 11 is coincident with the decay rate of the dienone. 

The use of dinitrogen pentoxide in the Ponzio reaction for the oxidation-iutration of oximes to em-dinitro groups has been reported by Russian chemists. Millar and co-workers extensively investigated these reactions and reported the synthesis of 2,4,5,7,9,9-hexanitrofluorene (2), a thermally stable explosive with an oxygen balance better than TNT. Other energetic materials containing gem-dinitro functionality were synthesized from the oximes of acetophenone, 4-nitroacetophenone, a-nitroacetophenone and 2-hydroxyacetophenone. 

C8H9NO2 2 -Hydroxyacetophenone oxime Gravimetric Metallochromic indicator V Fe 3... 

The condensation of 2-hydroxyacetophenone with benzaldehyde yielded exclusively 2 -hydroxy-chalcone, and the cyclization to flavanone was not observed. An investigation of the species adsorbed on the catalyst (289) suggested that CS condensation on the Ba(OH)2 surface occurs via a very rigid transition state, whereby the OH group of 2-hydroxyacetophenone is bonded to the catalyst surface and placed at great distance from the carbonyl carbon atom of the aldehyde, making the cyclization of 2 -hydroxy-chalcone to flavanone difficult. Deactivation of the catalyst was not observed in the presence of moderate amounts of organic acids, such as benzoic, acrylic, or trichloroacetic acid. 

Syntheses of 2- and 3-substituted chromones normally start from 2-hydroxyphenyl ketones. In the first of two examples, a route to flavone is shown in Scheme 5,10 using 2-hydroxyacetophenone (2-hydrox-yphenylethanone) and benzoyl chloride as starting materials. Initially, the phenolic group of the acetophenone is O-acylated by benzoyl chloride, using pyridine as a base (a Schotten-Baumann-type reaction). 

Both phenylhydrazones and imines derived from 5-halogeno-2-hydroxyacetophenones 510 were cyclized to the corresponding 4-methylene-substituted l,3-benzoxazin-2-ones 194 and 511 on treatment with 0.5 or O.bequiv of triphosgene under mild conditions (Scheme 96) <2003X8163, 2004SC71>. In the similar reactions of arylhydra-zones of 2-hydroxyacetophenones with 1 equiv of triphosgene, spiro-l,3-benzoxazine dimers were formed <2002JCM473>. 

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