Development Of A New Green Preparation Process For Benzofuran-2-(3H)-one

Benzofuran-2-(3H)-one is an important intermediate in pesticides,medicines,fine chemicals.It is an important block of the bactericide azoxystrobin((E)-[2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxypropenoic acid methyl ester).The production process has poor atomic economy and high environmental factors.Therefore,a new process for the development of the green preparation of benzofuran-2-(3H)-one is of great significance.In this paper,phenol was used as raw material to get allyl benzene ether from allyl chloride through Williamson etherification with a yield of 79.1%.Allylphenyl ether rearranged through Claisen rearrangement to produce o-allylphenol with a yield of 85.0%.Then o-allylphenol was oxidized to o-hydroxyphenylacetic acid by ozonation,and the yield was 55.9%.Finally,benzofuran-2-(3H)-one was synthesized through intramolecular esterification from o-hydroxyphenylacetic acid,with a yield of 99.4%.The total yield of the four step reaction was 37.4%.The preparation of o-hydroxyphenylacetic acid needs no expensive catalyst,and uses green oxidant ozone and hydrogen peroxide,and the process is green.In this paper,based on the optimization of batch reaction process,the synthesis of benzofuran-2-(3H)-one by microchannel reactor was studied.After screening,the second step Claisen rearrangement reaction achieved very good results.Under the condition of no solvent participation,the reaction temperature was 300 ?,the pressure was 6.0 MPa,the reaction time was 3 minutes,and o-allylphenol could be obtained with a conversion rate of ?99% and a selectivity of >95%.20 equivalents of 1,4-dioxane was used as solvent and 0.01 equivalent of p-toluenesulfonic acid was used as catalyst,the reaction was carried out at 180 °C and 1.5 Mpa for 100 minutes.The fourth step molecular intramolecular esterification yield was 39.6%.In the second step,the Claisen rearrangement reaction was shortened from 12 hours under batch conditions to 3 minutes in microreactor,the yield increased from 85.0% to 94.4%,and the reaction effect was improved very well.