Phenols acylation

HOUBEN - HOESCH Phenol Acylation Synthesis ol ketones (or aldehydes) by acylation ol phenols with nitriles (or ortho formates)... 

It has been reported [25] that PFR of ferrocene 96 of Scheme 29 produces the phenol acylated at the para position (97). The same authors have found that... 

Figure 3.5 Reaction scheme of the gas phase phenol acylation with acetic acid (AcOH) over HMFI at 553 K. Reprinted with permission from Industrial Engineering Chemistry Research, Vol. 34, Guisnet et al., Kinetic modelling of phenol acylation with acetic acid on HZSM5, pp. 1624-1629, Copyright (1995), American Chemical Society...

Advantage can be drawn from the positive effect of phenol on PA transformation into p-HAP to improve the yield and selectivity of p-HAP production.[82 84] Thus, with a HBEA zeolite the yield and selectivity for p-HAP passes from ca. 5 and 28 % respectively with cumene solvent to 24 and 60% with phenol as a solvent .[84] Again sulfolane was shown to have a very positive effect on the selectivity for p-HAP and limits the catalyst deactivation. To explain these observations as well as the effect of P and PA concentrations on the reaction rates, it was proposed that sulfolane plays two independent roles in phenol acylation solvation of acylium ion intermediates and competition with P and PA for adsorption on the acid sites.1831... 

Scheme 4.11. Construction of 1 — 2 aryl-branched poly esters via phenol acylation.

HOUBEN - HOESCH Phenol acylation 162 Huang Mnlon 426 Hubert 232, 299... 

A kinetic study of the acylation of phenol with phenyl acetate was carried out in liquid phase at 160°C over HBEA zeolite samples, sulfolane or dodecane being used as solvents. The initial rates of hydroxyacetophenone (HAP) production were similar in both solvents. However the catalyst deactivation was faster in dodecane, most likely because of the faster formation of heavy reaction products such as bisphenol A derivatives. Moreover, sulfolane had a very positive effect on p-HAP formation and a negative one on o-HAP formation. To explain these observations as well as the influence of phenol and phenyl acetate concentrations on the rates of 0- and p-HAP formation it is proposed that sulfolane plays two independent roles in phenol acylation solvation of acylium ions intermediates and competition with phenyl acetate and phenol for adsorption on the acid sites. Donor substituents of phenyl acetate have a positive effect on the rate of anisole acylation, provided however there are no diffusion limitations in the zeolite pores. 

Zuercher, W.J., Gaillard, S., Orband-Miller, L.A., Chao, E.Y., Shearer, B.G., Jones, D.G., Miller, A.B., Collins, J.L. et al. (2005) Identification and structure-activity relationship of phenolic acyl hydrazones as selective agonists for the estrogen-related orphan nuclear receptors ERRfJ and ERRy. Journal of Medicinal Chemistry, 48, 3107-3109. 

Phenol acylation with acetic anhydride over MFI catalysts is also very o-HAP selective, although with this acylating agent o-HAP would result from direct C-acylation of phenol rather than secondary transformation of phenyl acetate [21]. 

The whole argument is organized in four sections stoichiometric acylations, catalytic homogeneous acylations, catalytic heterogeneous acylations, and phenol acylations. It is structured according to the role played by the catalyst in the activation of reagents as well as in the different modes of regioselectivity encountered in the acylation of arenes, aromatic ethers, and phenols. 

Results from the literature suggest that direct phenol acylation and the Fries rearrangement are frequently competitive processes and difficult to characterize by the mechanistic point of view. Consequently, in Section 5.1, we include the synthetic process where the phenol substrate, the acylating agent, and the catalyst are mixed together in the starting reaction mixture aside from the specific reaction mechanism, whereas in Section 5.2 we include reactions involving phenyl esters. 

Sfudies on phenol acylation wifh acefic acid (AAC) over ZSM-5 zeolife confirm thaf fhe reacfion is very complicafed. The reacfion is carried ouf in a flow reactor charged wifh the zeolite catalyst at 280°C. The main... 

Studies on catalyst deactivation during phenol acylation with PA in the presence of BEA zeolite were performed by recovering the organic material entrapped into the zeolite following two methodologies ... 

While the first process represents a positive event because acetoxyaceto-phenones are convertible into HAPs and can give further intermolecular phenol acylation affording both ortho- and para-HAP, the second process produces ketene, which, being highly reactive, represents the most important source of coke responsible for heterogeneous catalyst deactivation. 

Neves, L, Jayat, R, Magnoux, R, Femt, G., Ribeiro, F. R., Gubelmann, M., and Guisnet, M. 1994. Phenol acylation unexpected improvement of the selectivity to o-hydroxyacetophenone by passivation of the external acid sites of HZSM5. /. Chem. Soc., Chem. Commun. 717-718. 

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