Phenols, acetyl derivatives

When the phenol contains a carboxylic acid group, e.g., m- or p-hydroxy-benzoic acid, the acetylated derivative will of course remain in solution as the sodium salt, but is precipitated when the solution is subsequently acidified. Salicylic acid, however, cannot be acetylated under these conditions. 

Hydroxythiophene also exists mainly in ketonic forms. Electrophilic reagents react either at oxygen or at C-5. O-Methyl and O-acetyl derivatives are obtained in alkaline solution, probably through intermediacy of the anion. In acidic solution, coupling with benzenediazonium ion, a characteristic phenolic reaction, is found to take place (Scheme 72). 

Cevanthrol, C jH gO, crystallises from benzene in plates, m.p. 197-8°, behaves as a phenol and gives an acetyl derivative, m.p. 138-9°. X-ray analysis (Bloxmt and Crowfoot indicates that it is a phenanthrene derivative, with a hydroxyl group, possibly at C . 

The complexes formed from salicylhydroxamic acid and acetylsalicylhydroxamic acid (104) with zinc show loss of one ligand proton and loss of two ligand protons respectively. The zinc complex of the acetyl derivative appears to show coordination via the deprotonated amide and phenolate oxygen of the ligand. IR studies are presented.849... 

Methyl 5-vinylsalicylate was prepared as shown in Scheme II (3). Friedel-Crafts acetylation of methyl salicylate gave the 5-acetyl derivative in 80% yield. Blocking of the phenol followed by NaBH reduction then provided methyl 5-(1-hydroxyethyl)acetyl-salicylate in an overall yield of 70%. The hydroxyethyl compound was dehydrated over KHSO at 225°C/0.2 mm, and the... 

Acyl-enzyme intermediates. Serine proteases are probably the most studied of any group of enzymes.229 Early work was focused on the digestive enzymes. The pseudosubstrate, p-nitrophenyl acetate, reacts with chymotrypsin at pH 4 (far below the optimum pH for hydrolysis) with rapid release of p-nitro-phenol and formation of acetyl derivative of the enzyme. 

Acetylation of the deoxybenzoin (439) under mild conditions gives the isofiavone directly rather than the acetyl derivative of the phenol (Scheme 151) (77MI22402). 

The bisbenzylisoquinoline alkaloid, isochondodendrine (33), (Fig. 5 and Table V) and its (9-methyl and O-acetyl derivatives have been studied by 13C NMR (23). The aliphatic carbon atoms of this symmetrical molecule were assigned by comparison to the benzylisoquinoline alkaloids and by the off-resonance spectrum. The oxygen substituent at C-8 caused a shielding of C-l. In the aromatic region of the spectrum C-9 and C-l2 had chemical shifts which remained essentially constant in all derivatives examined. Methylation and acetylation of the phenolic group produced characteristic shift changes which allowed the assignment of C-4a, C-6, C-7, C-8,... 

Two new phenolic aporphines derived from the discolored sapwood of Liriodendron tulipifera are (+)-lirioferine (20) and (+)-liriotulipiferine (21).16 (+)-N-Demethylthalphenine (22), previously known synthetically as a racemate, has now been obtained from Thalictrum revolutum DC.17 A new N-acetyl-noraporphine is ( —)-tuliferoline (23), present in Liriodendron tulipifera, together... 

Suspend 11 g (0.1 mol) of p-amino phenol in 30 ml of water contained in a 250-ml beaker or conical flask and add 12 ml (0.127 mol) of acetic anhydride. Stir (or shake) the mixture vigorously and warm on a water bath. The solid dissolves. After 10 minutes, cool, filter the solid acetyl derivative at the pump and wash with a little cold water. Recrystallise from hot water (about 75 ml) and dry upon filter paper in the air. The yield of p-hydroxyacetanilide, m.p. 169 °C (IX is 14g (93%). 

Phenoxy-substituted 2H, 8 -naphtha [l,2,3-de]-benz[/j]-2,8-quinolinedione (IIIC, R2 = hydrogen, R3 = CH3) was synthesized by cyclization of TV-chloro-acetyl-6-aminonaphthacenequinone in pyridine to the corresponding naphthacenepyrido-nyl-3-pyridinium chloride, with the subsequent reductive elimination of the pyridi-nium residue.39 The 3-acetyl derivative was obtained by the interaction of 6-amino-ll-chloro-5,12,naphthacenequinone with acetic anhydride in phenol in the presence of anhydrous sodium carbonate.39... 

Chemical methods for analysis of phenolic hydroxyl groups include determination of the increase in methoxyl content resulting from diazomethane methylation (Bjorkman and Person 1957), the increase in phenolic acetyl group content after acetylation (Lenz 1968, Mansson 1983), and low-molecular weight compounds derived from the degradation of phenolic structures (Chap. 5.2). The phenolic acetyl group of acetylated lignin may also be determined by an NMR spectroscopic technique (Lenz 1968, Robert et al. 1986) or by a selective deacetylation in pyrrolidine (aminolysis) (Mansson 1983). 

Acetylation of 179, followed by partial hydrolysis (phenolic acetyl group) and etherification (CH2N2), gave derivative 180. By hydrogenolysis, the C-16—C-17 bond in 180 was opened after etherification the resulting phenol was transformed to 181 (see Scheme 33). Under modified hydrogenation conditions that N-10—C-l 1 bond can be hydrogenolyzed as well. 

Aminothienyl-2-arsinlc acid results when the preceding acid is reduced by sodium amalgam in methyl alcohol solution. It crystallises in pale yellow, microscopic laminae, decomposing at 194° C. It is readily diazotised and coupled with amines and phenols, yielding highly coloured compounds. The acetyl derivative forms white prisms, M.pt. 134° C., with decomposition. 

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