Abstract
Bromination of (diethoxyphosphorylmethyl)acetylfurans with dioxane dibromide\t\t\t\t\tin the mixture of chloroform and acetic acid in presence of traces of hydrogen\t\t\t\t\tbromide at room temperature proceeds selectively at the methyl group of ketone\t\t\t\t\tdoes not involving phosphonate group. Obtained bromoacetyl derivatives were used\t\t\t\t\tfor alkylation of acetoacetic ester and cyclohexan-1,3-dione. Reaction of\t\t\t\t\t1,4-diketone prepared from acetoacetic ester with hydrazine hydrate in ethanol\t\t\t\t\tat room temperature leads to formation of furylpyrazines due to aromatization of\t\t\t\t\tintermediate azines by means of air oxygen.
Highlights
While the action of hydrogen bromide often leads to dealkylation of esters of furylmethanephosphonic acids
It is desirable to carry out bromination of phosphonomethylated acetylfurans with complex-bound bromine at low temperatures in media with low acidity
The signal of the proton of the methine group of acylmalonate in the 1H NMR spectrum is observed at 4.40 ppm, the signals of the protons of the chloromethyl group appear at 5.00 and 5.03 ppm in the 1 : 0.5 ratio
Summary
In the case of 3,4-disubstituted 3-bromoacetylfuran 5а, the yield is 72%, and its 2,4-disubstituted isomer 6а gives an alkylation product in 69% yield From that it follows that 3-bromoacetylfurans, in which the bulky diethoxyphosphorylmethyl group is in the position 4 or 5 of the furan ring, react more with acetoacetic ether than 2-bromoacetylfurans with remote substituents, and 2,3-disubstituted compounds are the least active regardless of the location bromoacetyl group. The signal of the carbon nucleus of the methylene group in the compounds under consideration is in the range 36.5–41.5 ppm, which corresponds to the value observed for the products of the alkylation of acetoacetic ester.
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