Preparation method of cajanin and substance with similar structure
A technology similar to kalinin, which is applied in the preparation of organic compounds, preparation of oxygen-containing compounds, chemical instruments and methods, etc., can solve the problems of no literature reports on the total synthesis of kalinin and its structural analogues
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Embodiment 1
[0042] Preparation of 2,4-Dihydroxy-6-methylbenzoic acid methyl ester (II, R 1 Is methyl)
[0043] Methyl acetoacetate (50g, 0.43mol) was dissolved in 300ml of ether, NaH (15.50g 0.45mol, 70%) was added at room temperature, after the addition, at this temperature, the ether solution of diketene (37g, 0.45mol) was added dropwise After the addition, react at room temperature for 3-4 hours, at which time the reaction system becomes yellow turbid liquid. The reaction was terminated, the reaction solution was added to 500 ml of ice-water mixture, the ether layer was separated, the water layer was extracted twice with 50 ml of ether, the ether layers were combined, washed with saturated brine, and dried overnight with anhydrous magnesium sulfate. Filtration, rotary evaporation to remove the ether, the residue was passed through the column with petroleum ether: ethyl acetate = 8:1 to obtain 35 g of white solid as the target product (yield 45%).
[0044] 1 H-NMR(400M, DMSO-d 6 ): δ (ppm) ...
Embodiment 2
[0046] Preparation of 2,4-Dimethoxy-6-methylbenzoic acid methyl ester (III, R 1 , R 2 All methyl)
[0047] Compound II (12g, 0.066mol) was dissolved in 50ml of acetone, potassium carbonate (27.3g, 0.198mol), methyl iodide (28g, 0.198mol) were added, and the reaction was heated and refluxed for 3h. The reaction was stopped. The reaction solution was added to 100ml of water and acetic acid Extract with ethyl ester (3*50ml), combine the organic layers, and wash the organic layers with 10% sodium hydroxide solution, 10% hydrochloric acid, and saturated brine in sequence. The organic layer was dried with anhydrous magnesium sulfate. After filtration, the solvent was removed by rotary evaporation to obtain a colorless oil, which was recrystallized with petroleum ether / ethyl acetate to obtain 13.5 g of colorless crystals (yield 97%).
[0048] 1 H-NMR(400M, CDCl 3 ): δ(ppm) 2.28(s, 3H), 3.80(s, 6H), 3.88(s, 3H), 6.31(s, 2H).
Embodiment 3
[0050] 2,4-Dimethoxy-6-bromomethyl methyl benzoate (IV, R 1 , R 2 All are methyl, X is bromine)
[0051] Compound III (10g, 0.0476mol) was dissolved in 50ml of carbon tetrachloride, protected by nitrogen, heated to reflux, and a mixture of NBS (8.5g, 0.0476mol) and BPO (0.11g, 0.476mmol) was added in batches. After the addition, reflux Reaction for 1h. The reaction was stopped, cooled, filtered, and the filtrate was spin-dried to obtain a light yellow solid, which was recrystallized from absolute ethanol to obtain 11.3 g of a white solid (yield 82%).
[0052] 1 H-NMR(400M, CDCl 3 ): δ (ppm) 3.85 (s, 3H), 3.93 (s, 3H), 3.96 (s, 3H), 4.66 (s, 2H), 6.47 (s, 1H), 6.74 (s, 1H).
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