The self-condensation reaction of methyl-4-chloroacetil-acetate in the presence of potassium carbonate Текст научной статьи по специальности «Химические науки»

92 CHEMICAL PROBLEMS 2020 no. 1 (18) ISSN 2221-8688

UDC 547.722 : 543.341

THE SELF-CONDENSATION REACTION OF METHYL-4-CHLOROACETIL-ACETATE IN THE PRESENCE OF POTASSIUM CARBONATE

G.G. Ibrahimova12

@

1Ganja State University 425, G.Aliyev ave., AZ 2001, Ganja, Azerbaijan; e-mail: [email protected]

2Baku State University Z.Xalilov str., 23, Baku AZ 1148, Azerbaijan Republic

Received 18.12.2019

The reaction of self-condensation of methyl 4-chloroacetylacetate in the presence of potash both in dimethylsulphoxide environment and without its participation was studied following which 1,4-dimetildicarboxylate-2,5-cyclohexadione and 1,4-dimethyl-dicarboxylatedihydroquinone were obtained, respectively. A mechanism for the formation of these compounds was proposed. With the participation of dimethylsulfoxide, the reaction proceeds in two stages: intermolecular condensation with subsequent intramolecular condensation and the participation of the active methylene unit and the chloromethylene fragment. Without participation of the solvent, in excess of potash, the obtained intramolecular condensation product during the intensive release of energy was aromatized to form 1,4-dimethyl dicarboxylate dihydroquinone.

Keywords: condensation, potash, dimethyl dicarboxylate acetone, methyl-4-chloro-acetylacetate, enol form, hydroquinone.

DOI: 10.32737/2221-8688-2020-1-92-96

Introduction

Polycarbonyl compounds and their derivatives are typical representatives of substances with an active methylene group, synthetic precursors of many natural and pharmacological compounds [1-6].

The interaction of polycarbonyl compounds with halogen alkanes provides an opportunity for alternative reactions progress, the direction of which can be changed by

choosing appropriate conditions and nature for reacting compounds [7, 8].

The low yield of alkylation products of dimethylacetone dicarboxylate (I) with mono-and polyhalogen alkanes [9, 10] gives reason to suggest that along with the alkylation reaction there is a competitive reaction involving only compound without an alkylating reagent.

Experimental part

The 1H and 13C NMR spectra were taken on a Bruker AV-300 [300 (1H) and 75 (13C) MHz] instrument, the internal standard was TMS. X-ray analysis was performed on a Bruker APEX II device.

1,4-dimethyldicarboxylate-2,5-cyclohexadione (1). 10 g (0.06) mol. of methyl 4-chloroacetylacetate was added with stirring to a mixture of 17 g (0.12 mol) of potassium carbonate in 50 ml of DMSO. The mixture was stirred for 3 hours at a room temperature and 10 hours at 60° C. The

reaction mixture was cooled, treated with water, after that there were formed suspended particles. It was filtered, and the filtrate was treated with ether, the extract was dried with Mg2SO4, the solvent distilled off, the yellow crystals of compound 1 precipitated out. The yield 14 g (52%), mp 152-153 ° C. Found,%: C 52.78; H 5.17 C10H12O6 Calculated,%: C 52.63; H 5.26

NMR 1H (5 mh): 3.2 s (2H, CH2), 3.8 s (3H, CH3O), 3.9 s (3H, CH3O), 7.45 s (1H, CH =), 9.8 s (1H, OH), 12.1 s (1H, OH). NMR 13C (5

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m.h.): 28.42 (CH2), 52.33 (OCH3), 53.07 (OCH3), 95.94 (CH), 118.00 (CH, enol), 120.05 (CH, enol), 151.32 (= CH), 168.00 (C=O), 171.36(C=O).

1,4-Dimethyldicarboxylatedihydro-quinone (2). A mixture of 40 g (0.28 mol) of potassium carbonate and 10 g (0.06 mol) of methyl 4-chloroacetylacetate was stirred for 3 hours at 15-20 ° C. From the coffee-coloured solution, yellow crystals of potassium dihydroquinone

1,4-dimethyl dicarboxylate precipitated. The precipitated crystals were treated with HCl; crystals of compound 2 precipitate from solution. Theyieldwas 7.8 g (41%), mp 158160 ° C. Found,%: C 52.68; H 4.57 C10H12O 6Calculated,%: C 53.09; H 4.42.NMR1H (5 m.h.): 3.86 c (6H, 2CH3O), 7.26 c (2H, 2CH= arom.), 9.66 c (2H, 20H). NMR13C, 5 m.h.: 53.10(OCH3), 118 (CH, arom.), 120.46 (CH, arom), 151.02 (=CH, arom), 167.81 (C=O).

Results and discussion

The structural similarity of dimethyl dicarboxylate acetone and methyl 4-chloro-acetylacetate suggests that the latter in an alkaline medium can undergo the self-condensation with the ester group, as it occurs with dimethyl 1,3-dicarboxylateacetone [10] and the participation of active chloromethylene fragment.

Of interest was the reaction of self-condensation of methyl 4-chloroacetylacetate in the presence of potash in two cases: in dimethylsulfoxide (variant A) and without the

solvent (variant B). Analysis of the product of self-condensation of methyl 4-chloroacetate in DMSO in the presence of potash showed that in the process of condensation the ester group was not affected and the reaction proceeds with the participation of the active methylene group and the chloromethylene unit to form 1,4-dimethyl dicarboxylate-2,5-cyclo-

hexadione (1). The mechanism of formation of the latter can be represented by the following scheme:

O

O

2 Cl

O'

O

The scheme shows a one-step process of the product formation 1, although it'd be preferable to assume that this process proceeds in two stages. At the first stage, intermolecular condensation occurs with the participation of the active methylene group and the chlorine of the methylene fragment. At the second stage, intramolecular condensation also occurred with the participation of the active methylene group and the chloromethylene fragment with the formation of product 1. Certainly, the

course of the reaction along this path was caused by the activity of the chlorine atom under the action of the adjacent carbonyl group. The structure of compound 1 was proved by 1H and 13C NMR spectra. According to NMR data, compound 1 mainly exists in the enol form. The alkylation reaction of compound 1, which was accompanied by the formation of an O-alkylated product, also confirms the enol structure of product 1.

Cl

O

Cl

\ K2CO3 / ДМСО

-H®

Cl

OH

O

\

OO

Cl

O

ON K2CO^ ДМСО

_ H

©

OO

O

O

— Cl O-

O

It should be noted that this condensation in the dimethyl dicarboxylate was formed. The

presence of potash without solvent proceeds further acidifying produced the corresponding

rapidly with the release of energy as a result of 1,4-dimethyl dicarboxylate of hydroquinone 2

which the potassium salt of hydroquinone 1,4- [10].

OO

H

KO

K2CO3 H +

-r lo

HO

OH

Fig. 2!H NMR spectra of compound 2

Fig.3. Molecular structure of compound 2

CO2CH3

1

CO2CH3

CO2CH3

CO2CH3

2

It should be assumed that methyl 4- energy release was aromatized into compound

chloroacetyl acetate was initially transformed 2. The structure of compound 2 was confirmed

into compound 1 under the action of potash by 1H and 13C NMR spectra (Fig. 2), as well as

which under conditions of potash excess with X-ray analysis (Fig. 3)

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METiL-4-XL ORASETiLASETATIN POTA§ MÜHiTiNDd ÖZÜOKSiDL d$Md REAKSiYASI BARADd

G.H. ibrahimova1'2

Ganca Dövlat Universiteti AZ 2001, Ganca $dh.,H.dliyevpr., 425 2Baki Dövldt Universiteti AZ 1148 Baki, Z.Xdlilov kûç., 23

Metil-4-xlorasetilasetatat potaçin içtiraki ila dimetilsulfoksid mühitindd va onun içtiraki olmadan özükondensld^md reaksiyasi naticasinda 1,4-dimetildikarboksilat-2,5-tsikloheksadion va 1,4-dimetildikarboksilat dihidroxinonun alinmasi öyranilmi^dir. Göstarilan birld^mdldrin alinma mexanizmi taklif edilmiçdir. Dimetilsulfoksid mühitindd reaksiya iki marhaladan ibaratdir-molekulalar arasi kondensla^ma va sonraki marhalada aktiv metilen zancir va xlormetilen

fraqmentin i^tirakila molekula daxili kondesla§ma gedir. Hdlledicinin i§traki olmadan, potagin artiq miqdarda oldugu halda molekula daxili kondesla§ma mdhsulu intensiv enerjinin ayrilmasi naticasinda aromatikila§ir va naticada 1,4-dimetildikarboksilat dihidroxinon alinir. Acar sözlw. kondesla§ma, pota§, dimetildikarboksilataseton, metil-4-xlorasetilasetat, enol, hidroxinon.

О РЕАКЦИИ САМОКОНДЕНСАЦИИМЕТИЛ-4-ХЛОРАЦЕТИЛАЦЕТАТА

В ПРИСУТСТВИИ ПОТАША

Г.Г. Ибрагимова1'2

1Гянджинский государственный университет AZ 2001,Гянджа, пр.Г.Алиева, 425 2Бакинский государственный университет AZ1148 Баку, ул. З.Халилова, 23 e-mail: [email protected]

Изучена реакция самоконденсации метил-4-хлорацетилацетата в присутствии поташа как в среде диметилсульфоксида, так и без его участия, в результате которой получены соответственно 1,4-диметилдикарбоксилат-2,5-циклогексадион и 1,4-диметилдикарбоксилат дигидрохинона. Предложен механизм образования указанных соединений. При участии диметилсульфоксида реакция протекает в два этапа -межмолекулярная конденсация с последующей внутримолекулярной конденсацией с участием активного метиленового звена и хлорметиленого фрагмента. Без участия растворителя, в избытке поташа образовавший продукт внутримолекулярной конденсации при интенсивном выделении энергии ароматизируется с образованием 1,4-диметилдикарбоксилат дигидрохинона.

Ключевые слова: конденсация, поташ, диметилдикарбоксилатацетон, метил-4-хлорацетилацетат, енольная форма, гидрохинон.