Ethyl bromomalonate

Commercial ethyl malonate distilled under reduced pressure and collected over a 30 range was used. 

Commercial bromine was dried by shaking with an equal volume of concentrated sulfuric acid. A slight excess of bromine is used to insure complete bromination. 

Ethyl bromomalonate is usually prepared without the use of a solvent.1 

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BenzOfurans from o-Hydroxylated Aromatic Carbonyl Compounds and Ethyl Bromomalonate... 

A mixture of 200 g. (1.9 moles) of anhydrous sodium carbonate (Note 1) and 300 g. (1.25 moles) of ethyl bromomalonate (Org. Syn. 7, 34) is heated for three hours in a i-l. flask (Note 2) immersed in an oil bath at 150-160° (Note 3). After the heating period, 300 cc. of xylene (Note 4) is added while the contents of the flask are still hot (Note 5). The solid is broken up carefully with a rod and the mixture is transferred to a 2-1. beaker. The reaction flask is then rinsed with a mixture of 100 cc. of xylene and 100 cc. of water. This washing is poured into the 2-1. beaker and an additional 600 cc. of water is added. The solid readily dissolves upon stirring. The liquid mixture is transferred to a separatory funnel, shaken well, and allowed to settle (Note 6). The lower aqueous layer is discarded (Note 7). The xylene layer is transferred to a i-l. distilling flask and distilled until the temperature of the liquid itself is 170°. The liquid residue is then transferred to a 500-cc. Claisen flask and distilled under reduced pressure. The forerun up to i7o°/r5 mm. is discarded. The product is collected at 170-23o°/i5 mm. (Notes 8 and 9). The distillate solidifies within about fifteen minutes. The yield is 150-160 g. (75-80 per cent of the theoretical amount). 

The mixture is heated in an open flask. Due to the high boiling points of ethyl bromomalonate and ethyl ethyl-enetetracarboxylate, there is but little loss by volatilization. On the other hand, the yield is lowered by the use of a condenser, presumably because the water formed by the reaction is kept in the reaction mixture with resultant hydrolysis of one or both of the esters. 

The synthetic implications of this discovery were slow to be exploited. Base-initiated dimerizations of 2-cycloalkenones, known to give crystalline solids,3233 remained puzzling for some time before conjugate additions were suggested to account for some of the possible products 34 indeed, the product of base-catalyzed dimerization of 4,4-dimethyl-2-cyclopentenone, which proceeds via a double Michael addition sequence, was not identified until 1969 (Scheme 2).35 An unanticipated cyclopropanation reaction of acrylaldehyde36 37 using ethyl bromomalonate and proceeding by means of a similar Michael addi-tion-Sw enolate alkylation represents an early synthetic use of tandem vicinal difunctionalization. 

When freshly prepared ethyl bromomalonate is used, the temperature of the mixture may rise spontaneously to 140°. In such event no heat should be applied until the temperature falls again. 

When a mixture of C60 (28.8 mg), ethyl bromomalonate and Na2C03 in 1 1 1 molar ratio was vigorously milled for 30 min, monoadduct 2 was obtained in 51% (81% based on consumed C, ) yield together with 7% (12% based on consumed Cgo) of bisadducts. 

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