Phthalide, from phthalic anhydride

From phthalic anhydride similarly dimethyl-, diethyl-, and dipropyl-phthalide are obtained ... 

Phthalides and phthalic anhydrides are extremely common components in a huge variety of polymers, and are prepared using many chemical processes. There are over 1300 references to polymers derived from phthalic anhydrides in the Registry File of Chemical Abstracts. Phthalic anhydride itself is used in polyester resins but there are also many examples of polyimides that are derived from related anhydrides. In this section, a few examples representing a range of structure and polymerization process are presented. 

It will be recalled that in the case of succinyl chloride both of these forms are obtained, but mostly the symmetrical (p. 282). Now from phthalic anhydride only one phthalyl chloride is obtained. This chloride acts like the unsymmetrical succinyl chloride, not like the symmetrical. The positive proof, however, that phthalyl chloride is the unsymmetrical compound is the following Sodium amalgam reduces phthalyl chloride by replacement of the chlorine with hydrogen. The compound formed is known as phthalide. This phthalide takes up water as anhydrides do and the product is hydroxy-methyl benzoic acid. 

Wainwright and Foster (1979) used F2<9j/r/<92 promoted with antimony oxide and potassium sulfate to study the effect of catalyst support materials on product distributions. The results were very similar to those of Vanhove and Blancard (1975) and differ only in the formation of carbon oxides from phthalic anhydride and phthalide. 

The phthalisoimidium salt (83), readily available from phthalic anhydride, reacts with Knoevenagel-type enolates to give the ylidene-phthalides (84). The related isoimidium perchlorate (85), on deprotonation with triethylamine, affords the butenolide (86) which with aromatic aldehydes and carbon disulphide forms the ene -type adducts (87) and (88) respectively. 

Condensation of an appropriately substituted phenylacetic acid with phthalic anhydride in the presence of sodium acetate leads to aldol-like reaction of the methylene group on the acid with the carbonyl on the anhydride. Dehydration followed by decarboxylation of the intermediate affords the methylenephthal-ides (12). Treatment of the phthalides with base affords directly the indandiones, probably via an intermediate formally derived from the keto-acid anion (13). The first agent of this class to be introduced was phenindandione (14) this was followed by anisindandione (1S) and chlorindandione (16). ... 

Acid Curing. Urea-formaldehyde resins and resol-phenol-formaldehyde resins can be acid-cured by wastes from the production of maleic anhydride [1902]. The waste from the production of maleic anhydride contains up to 50% maleic anhydride, in addition to phthalic anhydride, citraconic anhydride, benzoic acid, o-tolulic acid, and phthalide. The plugging solution is prepared by mixing a urea-formaldehyde resin with a phenol-formaldehyde resin, adding the waste from production of maleic anhydride, and mixing thoroughly. 

The phthalide used by the submitters and by the checkers was a commercial product, obtained from E. I. du Pont de Nemours and Company, Wilmington, Delaware. This product is no longer available. Phthalide may be prepared in 82.5 per cent yields by hydrogenation of phthalic anhydride in benzene at 270° under 3000 lb. pressure in the presence of copper chromite 1 or, in yields of 61-71 per cent, from phthalimide according to the procedure given in Org. Syn. 16, 71 Coll. Vol. 2, 1943, 526. 

The gas-phase reaction of N2O5 and naphthalene in an environmental chamber at room temperature resulted in the formation of 1- and 2-nitronaphthalene with approximate yields of 18 and 7.5%, respectively (Pitts et ah, 1985). The reaction of naphthalene with NOx to form nitronaphthalene was reported to occur in urban air from St. Louis, MO (Randahl et ah, 1982). The gas-phase reaction of naphthalene with OH radicals yielded phthalaldehyde, phthalic anhydride, phthalide, 1,4-naphthoquione, cis- and rra/J5-2-formylcinnamaldehyde, and 2,3-epoxy-1,4-naphthoquinone. 

Hydrogenation of phthalic anhydride over copper chromite afforded 82.5% yield of the lactone, phthalide, and 9.8% of o-toluic acid resulting from hydrogenolysis of a carbon-oxygen bond [1015]. Homogeneous hydrogenation of a,a-dimethylsuccinic anhydride over tris(triphenylphos-phine)rhodium chloride gave 65% of a,a-dimethyl- and 7% of )S,)S-dimethyl-butyrolactone [1016]. 

Electrochemical reduction of phthaloyl dichloride (73) at a carbon or mercury cathode in acetonitrile containing TEAP led to a complex array of products. Six cathodic waves observed in the CV for the reduction of phthaloyl dichloride arise from the reductions of different electrolysis products, as well as from hydrolytically formed phthalic anhydride (74),. caused by the presence of residual water in the solvent/supporting electrolyte (equation 45). From controlled potential electrolyses of phthaloyl dichloride, a variety of products including 3-chlorophthalide (75), phthalide (76), biphthalyl (77) and dihydrobiph-thalide (78) can be obtained69,70. Reduction of glutaryl dichloride (79) at a mercury cathode in acetonitrile containing 0.1M TEAP results in the formation of 5-chlorovalerolactone (80) and valerolactone (81) as minor products, and a polymeric material (equation 46)68. 

Pseudoesters, for example, 221, in which the alcohol portion is a fragrance (such as geraniol), have been developed for the slow release of scent. Alkaline hydrolysis of compound 221 requires time so that the rate at which scent is released is prolonged over that of simple evaporation <2001J(P2)438>. A similar approach involves the preparation of acyclic esters 222 and 223 from phthalide 224 and phthalic anhydride 225, respectively. In this case, the slow release of fragrance is the result of an intramolecular transesterification processes <2003USP20030148901>. 

Multibed tubular reactors to study o-Xylene oxidation have been used by McLean (in Wainwright and Foster, 1979) the catalyst is similar to that used by Boag (in Wainwright and Foster, 1979). The network differs in that McLean shows that the phthalic anhydride is formed almost exclusively from phthalide whereas Boag has indicated that this step does not occur. 

Calderbank et al. (1977) and Chandrasekharan and Calderbank (1979, 1980) studied the reaction over various commercial V20 tTi02 catalysts at low concentration and over a relatively wide temperature range (370-550°C). The main products identified are phthalic anhydride, o-tolualdehyde, phthalide, carbon monoxide and carbon dioxide. No maleic anhydride was detected. The combustion products were postulated to be formed only from o-Xylene and phthalic anitydride. Chandrasekharan and Calderbank (1980) have used a tube-wall catalytic reactor using two different catalysts. The main products identified over both catalysts were phthalic anhydride,... 

Novella and Benlloch (in Wainwright and Foster, 1979) studied u-Xylene oxidation using silica supported vanadium catalyst promoted by K2S0 in a fluidized bed in the temperature range 310-370 C. They isolated the same reaction products as Simard et ai. (in Wainwright and Foster, 1979), but proposed the formation of the oxides of carbon from u-tolualdehyde and phthalic anhydride as well as from <5>-Xylene. This model and that proposed by Simard et ai are notable for the absence of phthalide in the reaction products. 

Evidence for the formation of maleic anhydride only from the C-atoms of the aromatic ring has been obtained by Blanchard and Vanhove, who found no incorporation of radioactivity in the maleic anhydride formed from the oxidation of o-xy ene (methyl- C) or phthalic anhydride (- CO-) over V2O5 at 420-470 °C. A subsequent investigation by these authors was undertaken to elucidate the reaction pathways involved in the formation of the intermediates o-tolualdehyde, o-toluic acid and phthalide. A competitive oxidation of inactive o-methylbenzyl alcohol and o-xylene (methyl-... 

More than 10 years after the establishment of the acetalization process, electrochemists at BASF have searched for a compatible reductive process that can be run instead of the hydrogen evolution. What they have found is the reduction of phthalic acid dimethylester to phthalide [8] (Fig. 2). Phthalide is a compound that was up till then generated by classical catalytic hydrogenation from phthalic acid anhydride [7]. Part of the process development has been to fit the paired electrosynthesis in the same capillary gap cell like the acetalization of the toluene derivatives. 

The method of Leupold was used to prepare 3-( -nitrobenzyli-dene)phthalide in a 42% yield by the condensation of phthalic anhydride with 2 -nitrophenylacetic acid in the presence of potassium acetate m.p. 227-229 C (lit m.p. 222 C). The nitro compound was reduced by the conventional stannous chloride reduction to give 3-(p -aminobenzylidene)phthalide in a 64% yield. Recrystallization from aqueous acetone gave pale yellow needles m.p. 233 C. 

According to this new reaction network, the starting material is converted to the wanted product PA by three parallel routes via phthalic aldehyde and phthalic acid (reactions 8,9,10), via tolylic acid and phthalide (reactions 5,6,7) and via phthalide (reactions 4 and 7). Phthalic anhydride when formed is very stable but it is converted in part via bencoic acid (reaction 26) over a rather complex reaction scheme to maleic anhydride (MA). Maleic anhydride is formed directly from o-xylene via tolylic aldehyde (reaction 1) and toluene (reaction 11) by two routes and via dimethylben-zochinone (DMBQ) (reaction 15). Toluene and DMBQ are converted over a series of reaction steps to acetic acid. The main by-products, CO and CO2, are predominantly formed directly from o-xylene according to this mechanistic study. 

Phthalides.—Substituted bromobenzenes (96 R = Br) can be carbonylated in the presence of catalytic amounts of Pd(OAc)2 to give phthalides (97 n = 1) and other lactones (97 n = 2, 3) in yields ranging from 42— 70%. (For much the same reaction, see ref. 94). Alternatively, a sequence of thallation [T1(02CCF3)3] and Pd"-catalysed carbonylation can be used to convert benzyl alcohols (96 R = H) into lactones (97). ° The latter method can also be used to prepare phthalic anhydrides from benzoic acids. Presumably both methods will be largely restricted to symmetrical substrates. The dianions (98) can be obtained from the parent benzyl alcohols using Bu"Li in hexane at 0 C they react with CO2 to give good yields of 7-methoxyphthalides. ... 

A somewhat more recent paper [21] reports on another synthesis of 1, this time directly from 1,3-dihydro-benzo[c]thiophene-5-oxide (2), by oxidation with N-chlorosuccinimide or by treatment with sulfuric acid. This removes one step from the original synthesis. In addition, direct oxidation of 5 with N-chlorosuccinimide also gave polyisothianaphthene (1) [21] in a reaction similar to that reported by Jen and Elsenbaumer [17]. A direct one-step synthesis of 1 has been reported [22] that involves the reaction of phthalic anhydride (or phthalide) with phosphorus pentasulfide at temperatures above 120°C. Doping with NO SbF6" gave maximum conductivities of 10 S/cm. 

Oxidation, also partial, of methyl to carboxyl groups—Phthalic acid anhydrides from phthalides s. 16, 228 benzoic acid s. G. Messina, Hydrocarbon Process Petrol. Refiner A3 (11), 191 (1964) C. A. 62, 2733g... 

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