Background and overview[1][2]
Dimethylphenylethyl alcohol (DPC for short) is a synthetic fragrance with a strong natural floral aroma, exuding the fragrance of lilac and rose, with a soft and attractive smell. It can be used as the main raw material for blending various floral and novel flavors. Imported from abroad in recent years. Synthetic DPC generally uses phenylethyl alcohol, benzaldehyde or halobenzene as raw materials. Recently, Hu Liangbin et al. reported an improved synthesis method using benzaldehyde as raw material and using a new catalyst. Citterio et al. found that titanium trichloride can catalyze the conjugate addition reaction of diazonium salts and α,β-unsaturated compounds.
Methyl phenethyl alcohol
Preparation[2]
1. Preparation of diazonium salt
In a 50mL beaker, add 18mL of 24% hydrochloric acid solution. Add 4mL of aniline with stirring. Use an external ice-water bath to cool to zero degrees Celsius, and slowly drip in a solution of 3.29 (0.046 mol) sodium nitrite and 9 gmL water through a dropping funnel to obtain a light yellow diazonium salt solution, which is frozen for later use.
Preparation of 2.4-phenyl-2-butanone
Install a magnetic stirring rod and air guide tube on a 500mL three-necked flask, and add 90mL (0.10mol) titanium trichloride solution. At this time, slowly add 70mL of N,N-dimethylformamide under ice-water cooling and stirring, add 6mL (0.07mol) methyl vinyl ketone with a syringe, and then add ice-cold diazonium salt solution dropwise. After a few minutes, the solution begins to release nitrogen, and the dropping speed is maintained so that the nitrogen bubbles are 1 to 2 bubbles/s. After adding the diazonium salt, continue stirring in the ice bath for 10 minutes, then remove the ice bath, and stir the reaction solution at room temperature for 1 hour. Add 50mL ether and separate the organic layer. The aqueous layer was extracted with diethyl ether, the extracts were combined, washed with 3% sodium carbonate aqueous solution and water in sequence, and dried over anhydrous magnesium sulfate. The solvent was evaporated and distilled under reduced pressure to obtain a light yellow liquid.
Preparation of 3.3-benzene antioxidant 168-yl ethyl propionate
After the reaction of 4mL (0.043mol) aniline, 90mL (0.10mol) titanium trichloride solution and ·7mL (0.07mol) ethyl acrylate, 2.2g of yellow oily liquid was obtained. Yield 30%.
4. Preparation of dimethylphenylethyl alcohol (DPC)
Synthesized from ethyl 3-phenylpropionate. Put 500mg (35mmol) magnesium chips and 25mL anhydrous ether into a three-necked flask equipped with a reflux condenser and a dropping funnel, and add dropwise 5.89 (40mmol) methyl iodide and Prepare a Grignard reagent with a solution of 10 mL anhydrous ether. A mixture of 1.89 (10 mmol) 3-phenylpropionic acid ethyl ester and 5 mL diethyl ether was added dropwise while cooling in an ice bath. After the addition is completed, the water bath is refluxed for 1 hour. Then cool it with an ice-salt bath, and pour the reaction mixture into a mixture composed of 50g ice and 1mL concentrated sulfuric acid while stirring. Extract with ether alcohol, separate the ether layer, and extract the water layer with 2x20mL ether. Combine the extracts and wash with sodium bicarbonate aqueous solution and saturated brine in sequence. Dry over anhydrous magnesium sulfate and evaporate the solvent. Use silica gel column chromatography and elute with diethyl ether-petroleum ether (3:7) to obtain 2.2g of dimethylphenylethyl alcohol as a light yellow oily liquid.
Main reference materials
[1] Zhang Hesheng, Chen Jiawei, Yang Zhuo, & Yang Guichun. (1991). New synthesis method of dimethylphenylethyl alcohol. Chemical Reagents (3), 185-186.
[2] Zheng Gengxiu, & Wang Qiufen. (1995). Process improvement of one-step synthesis of methylethylbenzyl alcohol. Liaoning Chemical Industry (3), 30-31.
