2,4,6-trimethylbenzoylphenylphosphinic acid ethyl ester- Reaction / Application on synthetic works

2,4,6-Trimethylbenzoylphenylphosphinic acid ethyl ester is a photoinitiator for UV curable coatings. It is also an important organic intermediate to synthetize substituted benzoylphenylphosphinic products.

The following example is about its application on the synthesis of a new radical photoinitiator [1]

To a solution of starting material (15.00 g, 47.4 mmol) in 2-butanone (80 mL) stirred at room temperature, anhydrous NaI (7.819 g, 52.2 mmol) was added. After 10 min, a pale orange solution was obtained. This solution was heated in an oil bath to 60°C and stirred at this temperature for 24h. The product started precipitating after approximately 10min. The suspension was cooled to room temperature and was filtered under reduced pressure, washed with cold 2-butanone (2×50mL) and diethylether (2×40mL) and dried on air. A white solid (10.6g, 34.2 mmol, 72 percent) was obtained, which was directly used in the next step.

The following example is about its application on the synthesis of a cylphosphine oxide photoinitiator [2]

119.57 g (0.378 mol) 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide was dissolved in 500 ml acetonitrile. 67.28 g (0.378 mol) N-bromosuccinimid and 7.84 g (0.0324 mol) benzoyl peroxide were added and the mixture was heated to reflux. The mixture was refluxed for three hours. The mixture was allowed to cool down to room temperature and the solvent was removed under reduced pressure. The crude mixture was dissolved in 3600 ml methylene chloride and pre-purified on a GraceTM resolve RS8O column using a gradient elution from methylene chloride to methylene chloride/ethyl acetate 93/7 to remove non eluting residues. 60 g of the crude 4-bromomethyl-2,6-dimethylbenzoylethoxyphenylphosphine oxide was isolated. 4-bromomethyl-2,6- dimethylbenzoylethoxyphenylphosphine oxide was purified by preparative chromatography on a ProchromTM LC 80 column, using KromasilTM 60A 10 pm as stationary phase and hexane-methyl tertbutyl ether (50/50) as eluent. 21.26 g 4-bromomethyl-2,6- dimethylbenzoylethoxyphenylphosphine oxide was isolated (TLC analysis on RevelerisTM RP C18-plates, supplied by Grace, eluent hexane- methyl tert butyl ether (50/50), Rf: 0.17)).

The following example is about its application on the synthesis of a long-wave absorbing photoinitiator [3]

Three-necked flask 80 ml 2-butanone, taken 31.6 g (0.1mol) 2,4,6- trimethyl benzoyl diphenylphosphine mixed with ethyl added sodium iodide 15g (0.1mol), stirred was heated to 65°C , continuously during the reaction a precipitate, reacted for 24 hours, separated by filtration after cooling, the liquid is a mixture of ethane and iodine of 2-butanone, after the fractionation may be reserved for other use. The resulting solid was washed with acetone, dried, dissolved in 150 ml deionized water at a concentration of 1M sulfuric acid and the solution is acidified adjusted to pH 1, after standing for several hours, a substituted aryl-formylphenyl acid crystallize completel , filtered, washed with water, and dried in vacuo. The product 2,4,6-trimethylbenzoyl phenyl phosphinate 26.1g, 90.6 percent yield. 

References

1.Roszkowski P, Sahin M, Ayalur-Karunakaran S, Gammer C, Schlögl S, Kern W, Krawczyk KK. Synthesis and evaluation of new radical photoinitiators bearing trialkoxysilyl groups for surface immobilization[J]. Polymer, 2017, 129:207-220. 
2.Agfa GN, Loccufier J. Acylphosphine oxide photoinitiators. WO2017/191043[P], 2017, A1. Paragraph 0257; 0258; 0259. 
3.Guangdong Bossin Novel Materials Technology Co., Ltd. Pang L. Based on epoxy compound, a phosphorus-containing group of the long-wave absorbing photoinitiator and its preparation method (by machine translation). CN103333202[P], 2016, B, Paragraph 0062; 0063. 

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