A New Process For Reducing Formylation Of Nitroaromatic Hydrocarbons And Its Application

Fine chemical intermediates play an important role in the chemical related industries and fields.They are not only the downstream products of basic raw materials,but also the substrates of fine chemicals,dyes and active products.At the beginning of the 21 st century,China has made fine chemical and other chemical related fields as a key area of development,which has effectively promoted the development of the quality and variety of fine chemical intermediates and technological progress.Under this background,this paper mainly studies the new technology of reducing formylation of nitro aromatics to produce aromatic formamides,and applies it to the synthesis of important 3,4-diaminobenzoic acid and4-methoxy-1,2-phenylenediamine,which are important intermediates of o-phenylene diamine,to develop a simple,efficient and low-cost synthesis process of two intermediates.The details are as follows:(1)A convenient and cheap catalytic reaction system was developed for the important aromatic formamide intermediates,that is,in the buffer system of formic acid and ammonium acetate,copper acetate was used as the catalyst,a new method of one-pot direct reduction and formylation of nitro aromatics for the synthesis of aromatic formamides.The optimum conditions for the synthesis reaction were as follows: using 20 mol% of copper acetate as the catalyst,DMF as the solvent and10:1 formic acid/ammonium acetate as the reduction system,the amount of formic acid is 9 times of the substrate nitro aromatics,at 140 ℃ for 6 h,the maximum yield of the target product reached 91%.This process provides a simple,green and economical pathway to synthesize various aromatic formamides.Moreover,the catalyst can be reused 5 times with almost no significant reduction in activity.The experiments of the universality of raw materials,the enlargement of sunstrates and the recycle of catalysts show that the synthetic process exhibits better practicability and provides a simple,green and economical strategy for the preparation of aromatic formamides.(2)The new synthetic process of aromatic formamides was applied to the preparation of 3,4-aminobenzoic acid,and a new approach for the synthesis of intermediate 3,4-aminobenzoic acid was developed,the process conditions of the key nitrification steps in the procedure were optimized.4-formylaminobenzoic acid was prepared form 4-nitrobenzoic acid by a one-pot direct reduction process,and then3-nitro-4-formylaminobenzoic acid was obtained by a key nitration step,and hydrolyze the formyl group to form 3-nitro-4-aminobenzoic acid.The target product3,4-diaminobenzoic acid was obtained by the reduction reaction of3-nitro-4-aminobenzoic acid.The total yield of the four step reaction was 65.7%.The synthetic approach exhibited the advantages of cheap raw materials,less reation steps simple process,lower production cost and higher total yield of the product.(3)A new process for the synthesis of 4-methoxy-o-phenylenediamine form aromatic formamides has been developed and applied to the synthesis of4-methoxy-o-phenylenediamine.4-methoxy-o-phenylenediamine was synthesized from 4-nitroanisole by four steps including reduction formylation,nitration,hydrolysis and reduction,and the total yield was 68.9%.The technological conditions of the nitration reaction steps and the selectivity of the products were also discussed.Compared with the usual synthesis method,the process showed significant advantages such as cheap and available raw material,few reaction steps,simple process,low cost and high total yield of the product.