Benzoylmalonate

Submitted by John A. Price and D. S. Tarbell.1 Checked by T. L. Cairns and C. L. Dickinson. 

Mixed benzoic-carbonic anhydride Note 7). In a 500-ml. threenecked flask, equipped with a low-temperature thermometer, an efficient sealed stirrer, and an adaptive joint carrying a drying tube and a dropping funnel, is placed a solution of 24.4 g. (0.2 mole) of benzoic acid (Note 8) and 20.2 g. (0.2 mole) of triethylamine (Note 9) in 200 ml. of dry toluene. The solution is cooled below 0° by means of an ice-salt mixture, and 21.7 g. (0.2 mole) of ethyl chlorocarbonate (Note 10) is added at such a rate that the temperature does not rise above 0° (approximate time for addition is 25-30 minutes). Triethylamine hydrochloride precipitates both during the addition and while the mixture is stirred for 15-25 minutes thereafter. 

The described procedure is essentially the same as that reported by Lund.2 A similar preparation has been described by Reynolds and Hauser.3 

Commercial malonic ester was redistilled at reduced pressure to give material with d 1.4047. 

The ether dissolves the crystalline cake which has formed on cooling. This releases unreacted material and vigorous reaction again sets in. 

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Diethyl benzoylmalonate has been prepared by treatment of the copper derivative of ethyl benzoylacetate with ethyl chlorocarbonate.9 It... 

Diethylamino-3-butanone, 37,18 3-Diethylaminopropionitrile, 36, 7 Diethylaniline, 31, 111 Diethylaniline hydrochloride, 31, 112 Diethyl benzalmalonate, 30, 84 N,N-Diethylbenzenesulfenamide, 35, 101 N,N -Diethylbenzidine, 36, 21 Diethyl benzoylmalonate, 37, 20 Diethyl bromoacetal, 35, 52, 53 Diethyl carbonate, 30, 44 Diethyl cetylmalonate, 34,13 Diethylchloroacetal, 34, 46 Diethylcyanamide, 36, 25 Diethyl A2-cyclopentenylmalonate,... 

Diethyl 2-benzoylmalonate was reacted with anilines to give diethyl (arylamino)phenylmethylenemalonates (6, R = H, 2-Me, 4-Me, 4-C1) in 28-38% yields (54JIC711). 

Benzoylation of (phenylamino)phenylmethylenemalonate (4) with benzoyl chloride in diethyl ether in the presence of sodium at reflux temperature gave the 2-benzoylmalonate derivative (1509) (36JCS428). 

Acylation of ester enolates can also be carried out with more reactive acylating agents such as acid anhydrides and acyl chlorides. These reactions must be done in inert solvents to avoid solvolysis of the acylating agent. The preparation of diethyl benzoylmalonate (entry 1 in Scheme 2.14) is an example employing an acid anhydride. Entries 2-5 illustrate the use of acyl chlorides. Acylations with these more reactive compounds can be complicated by competing O-acylation. /V-Mcthoxy-iV-methylamidcs are also useful for acylation of ester enolates. 

Mixed anhydride synthesis. For use of the reagent in peptide synthesis, see Butyl chloroformate. The principle involved is illustrated by a procedure for the preparation of diethyl benzoylmalonate (3). Benzoic acid is condensed with cathyl chloride in toluene in the presence of triethylamine to produce the mixed anhydride (I), and an ethereal solution of ethoxymagnesium malonic ester (2), prepared from mulunic ester, magnesium, ethanol, and a trace of carbon tetrachloride as catalyst, is added... 

Diethyl benzoylmalonate has been prepared by treatment of the copper derivative of ethyl benzoylacetate with ethyl chlorocarbonate.9 It has also been obtained by the action of benzoyl chloride on a mixture of malonic ester and sodium ethoxide 1benzoyl chloride and the ethoxymagnesium derivative.14 The present method has been described in a previous communication and is of interest as an illustration of the use of mixed carbonic anhydrides as acylating agents.8... 

Cyclisation in 68% yield at the benzylic position occurred when the substituted benzoylmalonic ester indicated was treated with 4 proportions of lithium di-isopropylamide in tetrahydrofuran at -16X to give in 68% yield ethyl 1,3-dihydroxy-8-methoxynaphthalene-2-carboxylate (ref. 157). 

Benzoylmalonates (129) are available in one operation from iodobenzene by carbonylation in the presence of diethyl methyl malonate, triethylamine and a ferrocene-based palladium catalyst. Yields of up to 80% are reported using CO pressures of 20 atm. at 120 °C. 

The preparation of diethyl benzoylmalonate (entry 12) represents the use of an acid anhydride, a function in which it is much more reactive than an ester, as the acylating agent. The reaction must be carried out in nonnucleophilic solvents to prevent solvolysis of the anhydride from competing with the desired reaction. Other limitations on the use of highly reactive acylating agents, such as acid anhydrides and acid chlorides, in reactions with enolates derive from the fact that O-acylation may be the dominant reaction. The magnesium salt of diethyl malonate (entries 12 and... 

An aq. soln. of the Na-salt of ethyl benzoylmalonate oxime refluxed 10 min., distilled until iodoform test is no longer positive, then concentrated under... 

Preparation by hydrolysis of diethyl 3-acetoxy-5-methyl-benzoylmalonate with concentrated sulfuric acid in boiling aqueous acetic acid (70%) [2122]. 

Acylmalonic acid esters. Diethyl malonate added to NaH covered with tetra-hydrofuran, after ca. 1 hr. when H2-evolution has ceased and a soln. is formed, benzoyl chloride added all at once, stirring continued 5-10 min., then poured into water -> diethyl benzoylmalonate. Y 72%.—Tetrahydrofuran is an excellent medium for condensation reactions. In it, sodio compounds are soluble, and active halogen compounds, e.g. acyl chlorides, react instantly. F. e. s. S.-O. Lawesson and T. Busch, Acta Ghem. Scand. 13, 1717 (1959). 

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