Patent GB-747970-A (GB)
Title: Process of preparing diene adducts
Filed: 1953-06-30
Abstract: In a process for the production of diene adducts an a ,b -unsaturated carbonyl compound of the general formula <FORM:0747970/IV(a)/1> wherein (a) R1, R2, R3 and R5, which may be alike or different, represent a hydrogen atom or an alkyl or aryl group, and R4 represents a hydrogen atom or an alkyl, aryl or esterified carboxyl group, or (b) <FORM:0747970/IV(a)/2> represents a carbocyclic ring and R2, R4 and R5 are as defined above, or (c) <FORM:0747970/IV(a)/3> represents a carbocyclic ring linked through R2 and R5, and R1, R3 and R4 are as defined under (a) above, is reacted with an acylating agent and the intermediate product containing conjugated double bonds is reacted, without isolation from the reaction mixture, with a philodiene component which may be the same as or different from the acylating agent. All the reactants may be present together in the reaction space, or the a ,b -unsaturated carbonyl compound may be reacted in a first stage with the acylating agent and the philodiene component then added in a second stage to the reaction mixture.  If the philodienic compound is present in sufficiently large proportion, the first diene adduct can enter further diene reactions to yield secondary diene adducts.  Alternatively another philodiene can be used for the secondary diene synthesis.  As a further alternative an excess of the a ,b -unsaturated carbonyl compound can be used. Suitable a ,b -unsaturated carbonyl compounds are crotonal, 2-ethyl-2,3-hexenal, mesityl oxide, benzylidene acetone and 3,5 - dimethyl cyclohexenone.  As acylating agents acetic anhydride, acrylic anhydride, maleic anhydride, acetyl chloride, ketene and homologues of these compounds are mentioned.  Suitable philodienic compounds are acrylic anhydride, maleic anhydride, acrylonitrile, acrylic esters, crotonal, cyclohexenone and quinones and derivatives and homologues thereof.  The reaction may be effected in the presence of strong acid catalysts such as naphthalene sulphonic acids, chlorosulphonic acid, sulphuric acid and toluene-sulphonic acids, and of resinification and polymerization inhibitors such as thionine or methylene blue.  The reaction may be carried out in a solvent such as benzene or xylene, or an excess of one of the reactants such as crotonaldehyde, 2-ethylhexenal or acetic anhydride may serve as the solvent.  In examples: (1) maleic anhydride, crotonal and acetic anhydride are heated with p - toluenesulphonic acid and thionine to give 3-acetoxy-tetrahydrophthalic anhydride with some dihydrophthalic anhydride.  The product is converted completely to dihydrophthalic acid by boiling with dilute hydrochloric acid; (2) benzylidene acetone, acetic anhydride and maleic anhydride are heated with p-toluenesulphonic acid and methionine to give 4-acetoxy-6-phenyl tetrahydrophthalic anhydride which was esterified with methanol; (3) 2-ethyl-2,3-hexenol, acetic anhydride and maleic anhydride with b -naphthalenesulphonic acid and thionine are reacted to give 2 - acetoxy - 4,6 - diethyl - tetrahydrophthalic anhydride; (4) 3,5-dimethylcyclohexenone, acetic anhydride and maleic anhydride with thionine and naphthalene sulphonic acid are reacted to give endo-vinylacetate dimethyl hexahydrophthalic anhydride; (5) to heated p-quinone and acetic anhydride further acetic anhydride is slowly added to give hydroquinone diacetate, anthraquinone and hydronaphthoquinone diacetate; (6) butylidene-acetoacetic acid methyl ester, acetic anhydride and maleic anhydride, with methylene blue and sulphuric acid, are reacted.  On distillation aromatization with liberation of hydrogen takes place.  The product has a saponification number corresponding with the anhydride of methyl ethyl trimellitic acid monomethyl ester and the anhydride of propyl trimellitic acid monomethyl ester; (7) 2-ethyl-2,3-hexenal and acetic anhydride, with b -naphthalenesulphonic acid are refluxed, and the dienol ester reaction product then heated with acrylonitrile to give 2-acetoxy-3,5-diethyl tetrahydrobenzonitrile and 3 - acetoxy - 4,6 - diethyl tetrahydrobenzonitrile, which during the working up, yield under the influence of the sulphuric acid diethyl dihydroxy benzonitrile; (8) the reaction product of 2-ethyl-2,3-hexenal and acetic anhydride (sulphuric acid catalyst) is reacted with p-quinone to give diethyl acetoxy tetrahydronaphthoquinone.  Acetylation with acetic anhydride gives a diethyl naphthoquinone diacetate; (9) 2-ethyl-2,3-hexenal, maleic anhydride, xylene (solvent) with p-toluenesulphonic acid catalyst are heated to give diethyldihydrophthalic anhydride; (10) ketene is introduced into a solution of maleic anhydride, 2-ethyl-2,3-hexenal, thionine and b -naphthalene-sulphonic acid in benzene to give acetoxy diethyl dihydrophthalic anhydride, which during its distillation is converted to diethyl dihydrophthalic anhydride; (11) ketene is introduced into a mixture of maleic anhydride and b -naphthalenesulphonic acid dissolved in excess crotonal.  The product is mainly D 2,6-dihydrophthalic anhydride which becomes resinous on heating with the sublimation of phthalic anhydride.  In examples of the use of higher proportions of the philodiene, leading to a secondary diene synthesis, (12) mesityl oxide (1 mol.), acetyl chloride (1.2 mols.) and maleic anhydride (2 mols.) are reacted to give endovinyl dimethylcyclohexane tetracarboxylic dianhydride; (13) mesityl oxide (1 mol.) acetic anhydride (1 mol.) and maleic anhydride (2 mols.) with p-toluenesulphonic acid and thionine, are reacted to give endovinyl dimethylcyclohexane tetracarboxylic acid dianhydride; (14) 2-ethyl-2,3-hexenal (1 mol.), acetic anhydride (1.5 mols.) and maleic anhydride (2 mols.) with b -naphthalenesulphonic acid and thionine react to give diethyl endovinyl-cyclohexane tetracarboxylic acid dianhydride; (15) crotylidene diacetate (from the reaction of crotonal and acetic acid in the presence of p-toluenesulphonic acid) is reacted in stages with acetic anhydride to give endovinyl cyclohexane tetracarboxylic anhydride; (16) crotonal (1.65 mols.), ethyl acrylate (1.65 mols.) and acetic anhydride (5 mols.) are reacted in the presence of thionine, b -naphthalenesulphonic acid and cupric oxide to give dihydrobenzoic acid ethyl ester, and endovinyl cyclohexane dicarboxylic acid diethyl ester, which latter is converted to the di-octyl ester by alcoholysis; (17) the reaction product from 2-ethyl-2,3-hexenal, ethyl acrylate and acetic anhydride, i.e. diethyl dihydrobenzoic acid ethyl ester is reacted with an epuimolecular amount of maleic anhydride to give endovinyl-diethyl-hexahydrotrimellitic acid anhydride monomethyl ester, which is converted by reaction with ethyl alcohol to the corresponding triethyl ester; (18) maleic acid anhydride (1 mol.) crotonaldehyde (1 mol.) and acetic anhydride (1.9 mols.) are reacted, with a sulphuric acid catalyst, to give the dimer of dihydrophthalic acid anhydride.  In an example of the use of the a ,b -unsaturated carbonyl compound in excess, (19) crotonal (0.21 mols.), acetic anhydride (0.7 mols.) and p-quinone (0.185 mols.) are reacted, using a b -naphthalene sulphonic acid catalyst, to give anthraquinone.