Alkylation of CH-Acids with 3-Halomethyl Derivatives of Ethyl (Diethoxyphosphorylmethyl)furoates
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lation of CH-Acids with 3-Halomethyl Derivatives of Ethyl (Diethoxyphosphorylmethyl)furoates L. M. Pevznera,*, V. S. Zavgorodniia, and A. I. Ponyaeva a
St. Petersburg State Institute of Technology (Technical University), St. Petersburg, 190013 Russia *e-mail: [email protected] Received June 11, 2020; revised June 11, 2020; accepted June 21, 2020
Abstract—Alkylation at the carbon atom of the active methylene group of 3-halomethyl derivatives of phosphonocarboxylic acid esters of the furan series with acetylacetone, acetoacetic, malonic and cyanoacetic esters in an absolute ethanol–dioxane medium (1 : 10) in the presence of sodium ethylate leads to the formation of the corresponding monoalkyl derivatives. The obtained phosphonomethylated derivatives of 3-(furylmethyl)acetylacetone and ethyl 2-(furylmethyl)acetoacetate react with hydrazine hydrate to form phosphorus-containing derivatives of (furyl)(pyrazolyl)methanes and (furyl)(pyrazolonyl)methanes, respectively. The latter in chloroform exist exclusively in enol form. Keywords: СН-acids alkylation, 3-halomethylfurans, pyrazoles, pyrazolones, keto-enol tautomerism
DOI: 10.1134/S1070363220110092 Recently we have developed the protocol for alkylation of most widespread CH-acids with 2-halomethyl derivatives of phosphonocarboxylates of the furan series what permitted to synthesize starting substances for obtaining of hybride heterocyclic systems having in their structure the functionalyzed furan as well as the azole or azine cycles separated by the methylene bridge [1]. In the course of that work 4-substituted derivatives of 3,5-dimethylpyrazole and 4-methyl-5-hydroxypyrazole were synthesized. Developing the work in this direction we turned to investigation of recently prepared [2, 3] 3-halomethyl derivatives of phosphonocarboxylates of the furan series. The necessity of investigation of this type of compounds arises from the fact that substances having 3-furanyl fragment in their structure are widespread in nature and exhibit high biological activity [4]. Compounds 1–6 were used as alkylation agents. Their structure covers all possible variants of relative location of phosphonomethyl and ester groups in the molecule of 3-halomethylfurans. In some cases we failed to synthesize three-substituted compounds of needed structure, and because of that substances 3–5 containing ballast methyl group were used. Acetylacetone, ethyl acetoacetate, diethyl malonate, and ethyl cyanoacetate were used as CH-acids. In all cases the reaction was carried out in 1 : 10 mixture of absolute ethanol and dioxane at 90°C and the furan 1–6 to CH-acid molar ratio = 1.0 : 1.1 in
presence of 1.05 mol of sodium ethylate and 0.2 mol of potassium iodide per 1 mol of furan in the course of 10 h (Scheme 1). The alkylation products 1a–6d were isolated as yellow or light brown syrups decomposing below boiling points during vacuum distillation. Analysis of dependence of yield of the alkylation products on the structure of 3-halomethyl derivative shows that poorest results for all four CH-acids used wer
