Homophthalic acid anhydrides

Fulveneallenes and benzocyclobutenones from homophthalic acid anhydrides... 

A mixture of equimolar amounts of homophthalic acid anhydride, veratriylidene-methylamine, and methylene chloride refluxed 10 min., and the resulting soln. allowed to stand 1 hr. at room temp. -> ( )-rran -4-carboxy-3-(3,4-dimethyoxy-phenyl)-2-methyl-3,4-dihydro-l(2H)-isoquinoline. Y 96%. F. e. s. M. A. Haimova et al.. Tetrahedron 33, 331 (1977) N-condensed N-heterocyclics s. M. Cushman, J. Gentry, and F. W. Dekow, J. Org. Chem. 42, 1111 (1977). 

Homophthalic acid. This is a four-stage preparation with phthalic anhydride as the starting material ... 

Homofolic acid, 5,11-methenyl-tetrahydro-biological activity, 3, 327 Homofolic acid, tetrahydro-biological activity, 3, 327 Homoisoflavanones occurrence, 3, 722 thermoisomerization, 3, 722 thermolysis, 3, 728 Homolytic reactions heterocyclic compounds reviews, 1, 74 Homophthalic acid isocoumarins synthesis from, 3, 830 synthesis, 3, 830 Homophthalic anhydride isochroman-l-one synthesis from, 3, 860 20a-Homoporphyrin nomenclature, 1, 30 Homopterocarpin isolation, 4, 998 ( )- D- Homotestosterone synthesis, 1, 453 Homer-Emmons reaction chromene synthesis by, 3, 749 Hortiacine isolation, 3, 149 Hortiamine isolation, 3, 149... 

The first direct approach to a pentacyclic system, based on the condensation product 101 of tryptamine with a homophthalic acid or anhydride, was introduced by Clemo and Swan and extended to reduced and substituted homophthalates. Esterification of... 

Homophthalic acids are acylated by acid anhydrides in the presence of pyridine, producing 4-acylisochroman-l,3-diones (494) (80CB3927). Rearrangement to a 3-alkylisocoumarin-4-carboxylic acid (495) occurs in acid solution and may be accompanied by decarboxylation. 

The reaction of homophthalic acids or anhydrides with citral in the presence of pyridine yields reduced pyran-2-ones by means of an aldol condensation involving the activated methylene group of the acid. Dehydration is followed by an acid-catalyzed rearrangement to the pyran-2-one (Scheme 201) <79H(12)253). 

HOMOPHTHALIC ACID AND ANHYDRIDE (a-Toluic acid, o-carboxy-, and 2-benzopyran-l,3-dione)... 

B. Homophthalic anhydride. A mixture of 60 g. (0.33 mole) of dry homophthalic acid and 33.7 g. (31 ml., 0.33 mole) of acetic anhydride in a 200-ml. round-bottomed flask fitted to a reflux condenser by a ground-glass joint is refluxed for 2 hours. The mixture is cooled to about 10° for 30 minutes, and the solid anhydride is collected on a Buchner funnel with the aid of suction. It is washed with 10 ml. of glacial acetic acid and pressed, and as much of the solvent as possible is removed by suction. hc product is spread out on a porous i)latc for several hours... 

Homophthalic anhydrides can be prepared by the dehydration of homoph-thalic acid with add chloride, acid anhydride, phosgene, thionyl chloride, benzene sulfonyl chloride, ketene, phosphorous pentoxide, dicyclohexyl-carbodiimide, or J -carbonyldiimidazole. However, these methods are not always effective for the acid-sensitive and/or unreactive homophthaUc acid derivatives. We developed a very mild and efficient method for obtaining homophthaUc anhydrides using (trimethylsilyl)ethoxyacetylene [9] (Scheme 1). Thus the treatment of homophthaUc acid 1 with (trimethylsi-lyl)ethoxyacetylene 2 in inert solvents such as methylene chloride, 1,2-di-chloroethane, and acetonitrile gave the homophthaUc anhydride 3 in a quantitative yield accompanied by ethyl trimethylsilyl acetate as the only side product. The high purity homophthaUc anhydride 3 could be obtained for the next cycloaddition reaction just by evaporation to remove the reaction solvent and the formed ethyl trimethylsilyl acetate. The method is quite useful, and was also applicable to the syntheses of hetero-homophthalic anhydrides 4. 

A convenient and efficient route to isocoumarins has been described starting from readily available substituted indan-l-ones, which are first converted to the enol form with trifluoroacetic anhydride, then cleaved with ozone. Isocoumarin-4-carboxylic acid is easily prepared from homophthalic acid by addition of Vilsmeier reagent followed by hydrolysis. 

In a facile and rapid stereoselective, three-component, one-pot reaction, a series of cis-isoquinolonic acids 132 were synthesized using silica supported sulfuric acid to catalyze the reaction between homophthalic anhydride 133 with different aldehydes 134 and amines 135. This three-component cyclocondensation offers a variety of advantages including high yields, easy experimental work-up, and the use an inexpensive, non-toxic, readily available, and recyclable catalyst <06JHC187>. 

The ionic liquid [BMIM]BF4 was found to efficiently catalyze the three-component coupling reactions of aldehydes, amines, and homophthalic anhydride under ambient conditions to give the corresponding c/ -isoquinolonic acids in excellent yields with... 

Carboxybenzyl aryl ketones are formed together with the isocoumarin when homophthalic anhydride (isochroman-l,3-dione) is used to acylate aromatic molecules under Friedel-Crafts conditions (51JOC1064) and the 7-methoxy derivative behaves in a similar fashion (66JIC615). Some care in the choice of Lewis acid is necessary in view of the formation of the tropone derivative (504) in the acylation of hydroquinone (Scheme 181) (55JCS2244). 

The oriAo-benzoyl-benzoic acids readily yield anthraquinone and its derivatives (see p. 82). It may be noted that o-benzoyl-benzoic acid itself, with benzene and aluminium chloride, yields phthalophenone the same compound is made directly from phthalic anhydride by increasing the amount of the latter or by adding acetic anhydride. The same holds for p-toluoylbenzoic acid and ditoluoylphthalide. (Am. Soc., 43, 1965 J. C. S., 122, 539.) (For the use of carbomethoxylbenzoyl chlorides and of homophthalic anhydrides in these reactions, see Am. Soc., 43, 1950.)... 

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