Resorcinol, reactions Hoesch reaction

Preparation by reaction of m-chlorobenzo-nitrile with resorcinol (52%) (Hoesch reaction) [1256],... 

Obtained by reaction of 2,5-dimethoxy-phenylacetonitrile (m.p. 56-57°) with resorcinol (40%) (Hoesch reaction) [5531]. 

The Hoesch Reaction is employed for the introduction of the - COR group into the aromatic ring of phenol or a phenolic ether, and usually proceeds particularly readily with polyhydric phenols. If an ethereal solution of resorcinol (I)... 

An analogous reaction is the Houben-Hoesch reaction,(sometimes called the Hoesch reaction) using nitriles 7 to give aryl ketones 8. This reaction also is catalyzed by Lewis acids often zinc chloride or aluminum chloride is used. The Houben-Hoesch reaction is limited to phenols—e.g. resorcinol 6—phenolic ethers and certain electron-rich aromatic heterocycles ... 

The benzoylation of resorcinol to produce 2,4-dihydroxybenzo-phenone has been previously performed with benzotrichloride, which implies the coproduction of 3 mol of hydrochloric acid and consequently a large amounts of acid waste. " Alternative routes to 2,4-dihydroxyben-zophenone involve direct acylation of resorcinol with benzoyl chloride (BC) or the Hoesch reaction with benzonitrile, which also suffer from acid waste production. In a more ecoefficient approach, the reaction was performed with benzoic acid (BAC) in the presence of some solid catalysts, with a special focus on BEA zeolite (Scheme 5.9). The progress of the reaction in para-chlorotoluene is examined, and after 18 h, 2,4-dihy-droxybenzophenone (2,4-DHB) is isolated in 70% yield, together with 20% of resorcinol monobenzoate (RMB), 3% of resorcinol dibenzoate, 5% of BAC, and 2% of resorcinol. The fact that the concentration of resorcinol in the final mixture is somewhat lower than that of BAC is probably due to the preferred adsorption of the former. The process is then studied by using different substituted BACs the different conversions of 2-methyl-,... 

Important Note It is mandatory for Hoesch Reaction to maintain absolute anhydrous conditions therefore, the ether and the acetonitrile must each be dried and distilled before using in the synthesis, and the resorcinol should also be dried in a vacuum desiccator. 

The correspondingly substituted benzophenones are obtained in a yield not exceeding 35%, using substituted benzonitriles [20]. E. N. Zil -berman and N. A. Rybakova [21-23] modified the procedure for conducting the Hoesch reaction and S3mthesized a number of aromatic hy-droxyketones in 60-89% yield. According to the procedure they developed, hydrogen chloride is passed into an ether solution of the nitrile and zinc chloride for 2-3 hr at a temperature of 2-5°C, and then resorcinol is added. 

Also obtained (poor yield) by condensation of o-acetoxybenzonitrile with resorcinol in the presence of zinc chloride and hydrochloric acid in ethyl ether at 0° (Hoesch reaction), followed by hydrolysis of the intermediate compound obtained with boiling 0.5 N sodium hydroxide (<5%) [381]. In this reaction, the major compound was 3-hydroxyxanthone (18%). 

Obtained by reaction of p-chlorobenzo-nitrile with resorcinol in the presence of zinc chloride and hydrochloric acid in ethyl ether (Hoesch reaction) in ice during 24 h and hydrolysis of 4 -chloro-2, 4-dihydroxybenzophenone imide hydrochloride so formed (72%) with boiling water for 30 min (46%) [1253], (39%) [1256],... 

Preparation by reaction of p-(2-bromoethyl)-benzonitrile with resorcinol (Hoesch reaction) (53%) [1147]. 

Preparation by reaction of acetonitrile on resorcinol monomethyl ether (Hoesch reaction) (27%) [2301]. 

Preparation by reaction of acetonitrile with 5-heptyl-resorcinol according to Hoesch reaction (57%) [3623]. 

Also obtained by reaction of bromoacetonitrile on resorcinol with zinc chloride and hydrobromic acid in ethyl ether (Hoesch reaction) [4432,4433]. 

Preparation by reaction of chloroacetonitrile on resorcinol with zinc chloride (Hoesch reaction) (90%) [4590], (82%) [4591] or with triflic acid (trifluoromethanesulfonic acid) (23%) [4592]. 

COCF3 Preparation by reaction of triflnoroacetonitrile on 4-ethyl-resorcinol (Hoesch reaction) (71%) [4679]. m.p. 99° [4679]. 

Obtained by reaction of o-methylphenoxyac- — / etonitrile with resorcinol (Hoesch reaction) jjQ. (82%) [5021],... 

Also obtained by reaction of hydroxyacetonitrile with resorcinol [4845], (41%) (Hoesch reaction) [5087]. 

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