Optimization On Synthesis Technology Of Benzofuranol

Benzofuranol is a most important pesticide intermediate in the synthesis of various chemical compounds such as :carbofuran,carbosulfan,benfuracarb and so on, which is a fine chemical product with high value-added. At present, it is produced mainly from catechol and methallyl chloride at home and abroad, this technological process includes etherification reaction, rearrangement reaction and cyclization reaction.This technological process has an advantage in easily obtaining material, short process and a rational yield. whereas in the etherification reaction, the selective monoetherification of one hydroxy group present on the catechol serious difficulties because each of these two hydroxyl groups can participate in reaction. Under above-mentioned conditions, the yield of etherification reaction with 81% was achieved. As for rearrangement reaction, because of high reaction rate and without catalyst,it is difficult to control the reaction,so some by-product will be abtained easily. Besides, in the cyclization reaction, the rate of reaction is slow, due to these two reaction can process in the same reaction conditions, we always call them cyclization reaction for short. In this reaction, the conversion is over 98%, but the yield is only 75%.Consequently, the overall yield of benzofuranol is only about 60%.Firstly, by Consulting a lot of references and choice of operating conditions, the HPLC quantitative analysis method is developed to analysis the material, intermediate product and benzofuranol.Secondly, the process conditions of etherification reaction are optimized through analysing the specific reaction process and the effect of some factors on the yield of o-methallyloxyphenol, such as material ratio,reaction time,reaction temperature and time of dropping, the suitable conditions of etherification reaction are found as follows: the molar ratio of catechol to methallyl chloride to 2-methoxyethanol to sodium carbonate is 1.0:1.2:8.0:0.6; the reaction temperature was 98℃～105℃;the reaction time was 3.0h;and the time of dropping of 2-metho- xyethano was 90 min.After the reaction was stopped, the reaction mixture was cooled to room temperature, filtered and distilled at a reduced pressure to obtain o-methallylo- xyphenol mixture.Under these operation conditions, the selectivity of etherification reaction is over 96%, and the yield of o-methallyloxyphenol is about 82%.Thirdly, the technology for solvent extraction and separation of the unreact- ed catechol in the etherification reaction through a great number of experiments.In this process, distilled water and xylene were used as extractive agent, the unreacted catechol were recycled through multiple extraction. Then the water layer that contained catechol was distilled at a reduce pressure to removal of water. The recycled catechol was used for recycling utilization. It was proved that there were no negative influence off reaction through some contrastive experiments. The overall recovery of catechol was above 80%, the overall yield reached 90%, which is 10% higher than industrial level .Finally, the process conditions of cyclization reaction was researched and analyzed, and the optimized conditions are obtained. Under the suitable conditions, the yield reached 77%.