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N-alkyl phthalimide compounds synthesis of aliphatic primary amines and alpha-amino acid is an important intermediate in organic synthesis occupies a very important position. In recent years, there are some reports of research on all kinds of N-alkylation of amines or amides. N-alkylation of phthalimide study also reported, such as KF-Al 2 O 3, etc. as a catalyst, benzyl bromide for the debenzylation reagent in a suitable solvent under reflux for several hours, it is possible to obtain better yield, but the reaction rate to be further improved; reported under microwave irradiation can also quickly realize phthalimide N-benzyl.

In recent years, ultrasonic radiation technology is widely applied in organic synthesis. Our group in the ultrasonic irradiation conditions, the use of relatively inexpensive benzyl chloride as raw materials, using potassium carbonate as a catalyst, tetrabutylammonium iodide as phase transfer catalyst, synthesis of N-benzyl-phthalimide fast response, simple operation, high yield and purity than.

1 Experimental 1.1 Reagents and Instruments phthalic imide chemically pure; other reagents were of analytical grade.

Melting point determined by the WRS-1A digital melting point apparatus; ultrasonic device KQ-250B-type Ultrasonic cleaner; elemental analysis determined by the United States PE-2400 elemental analyzer; hydrogen spectrum by Varian, USA MercuryPlus300 nuclear magnetic resonance spectrometer (300 MHz , CDCl 3) determination, TMS as internal standard.

Synthesis of 1.2N-benzyl-o-phthalimide conical flask, phthalimide 2.2 g (0.015 mol), the benzyl chloride 2.5ml (0.02 mol), 10 ml of DMF, tetra-n-butyl iodide the ammonium hydroxide 0.3g, 10 mL of water, potassium iodide, 0.3 g of potassium carbonate 1g. placed in an ultrasonic cleaning device cleaning equipment, adjusting the temperature of the water bath to 80 ° C, ultrasonic radiation for 30 minutes, remove the filter. The filtrate was added 15mL5% sodium hydroxide solution, there are a large number of white floc is generated, allowed to stand, filtered, washed crude product was recrystallized from 95% ethanol to give a white needle-like crystals 3.38g, yield 95.3%. Product mp: 115.4 ° C (115 to 116 ° C) reported consistent. 2 Results and discussion 2.1 The reaction time for the reaction of a fixed amount of raw materials (phthaloyl imide 2.2G, 2.5 mL of benzyl chloride, the same below) and other reaction conditions, the reaction time was changed to study the quantity of product. The results showed that the optimum reaction time for 30min, the reaction time is too long, due to the dispersion and emulsifying action of the ultrasonic wave and a phase transfer catalyst, the product was difficult to crystallization.

2.2 fixed amount of raw materials and other reaction conditions of the reaction as a catalyst, the catalytic effect of the type of catalyst to be explored. The experiments show that the K 2 CO 3 Preferably, the catalytic effect of Al 2 O 3 in the reaction is not catalysis. After exploring K 2 CO 3 dosage of 1 g.

2.3 Temperature effect on the reaction of a fixed amount of raw materials and other conditions, changing the reaction temperature, the effects of temperature on the reaction. The experiment found that the yield increased with increasing temperature to 80 ° C reaches a maximum.

2.4 potassium iodide on the reaction of a fixed amount of raw materials and other reaction conditions, to investigate the amount of potassium iodide on the reaction. It was found that potassium iodide was added in the reaction system, there is a great role in promoting the reaction, the optimum amount of potassium iodide for 0.3g because iodide ions have a good nucleophilic ability and leaving ability, reaction with poor reactivity, but cheaper benzyl chloride as raw materials, will get the results.

2.5 a phase transfer catalyst on the reaction for the heterogeneous reaction due to the start of the reaction, and therefore adding a phase transfer catalyst is tetrabutylammonium iodide to improve the yield, but not too much, otherwise the course of the reaction will cause the emulsification, the product is not easy to suction . Fixed amount of raw materials and other reaction conditions, the study found that: (C 4 H 9) 4 NI optimum dosage to 0.3 g.

Of 2.6N-benzyl phthalimide characterization Elemental Analysis for C 15 H 11 O 2 N Found% (theoretical value,%): C 75.87 (75.94), H4.71 (4.67), N5 .91 (5.90) 1 HNMR (300MHz, CDCl 3), δ: 4.85 (s, 2H, CH 2), 7.30 ¯ 7.83 (m, 9H, C 6 H 5, C 6 H 4).

3 Conclusion In order to enable higher rates of reaction of phthalimide completely cheaper benzyl chloride in the ratio of raw materials in a slight excess (approximately 1:1.3).

The use of ultrasonic radiation to a very high yield (95.3%) can be reached in a short time (30 min), under reflux conditions to achieve a similar yield (92.5%) 6h need to shorten the reaction time of more than a dozen times, indicating ultrasonic radiation on the phthalimide N-benzylation good role in promoting. The structure of the product by elemental analysis, NMR and melting point is further confirmed.

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