Research On The Product Selectivity Influenced By Reaction Conditions In Synthesizing The Meso Substituted Asymmetric Porphyrins

Porphyrins have broad application in the fields of analytical chemistry, medicinal chemistry, molecular recognition and photoelectrochemistry etc, owing to its special structure of the conjugate plane. The meso substituted asymmetric porphyrins, as a branch of porphyrins, also play an important role in these fields.In the past few decades, although people had made a breakthrough in synthesis of meso substituted asymmetric porphyrins, nowdays the synthesis methods of the meso substituted asymmetric porphyrins are still very attractive for scientist. Among many synthesis methods of the porphyrin, "Adler" and "Lindsey" methods have less steps and simpler operation. However, it is worth noting that the crude products are complexs, and the selectivity of required porphyrin is the key to the success or failure of the experiment. Therefore, inversitagation of the crude products selectivity has a certain practical and scientific significances.In this paper, both "Adler" and "Lindsey" for synthesis of the meso substituted asymmetric porphyrin are investigated,using benzaldehyde, p-methoxybenzaldehyde and pyrrole as raw materials. By means of studying reaction conditions response to the product selectivity,we obtained some selectivity-controlled methods for the synthesis of the meso substituted asymmetric porphyrin.The details are as follows:1. The application and synthesis methods of the meso substituted asymmetric porphyrin are summarized;2.The high-performance liquid chromatography qualitative and quantitative analysis methods for meso substituted asymmetric porphyrins was established,and was applied to investigation of product selectivity influenced by reaction conditions. As for the Lindsey method,the ratio of raw materials, additives (alcohol and salt), catalyst concentration, reaction time were studied. As for the Adler method, the ratio of raw materials and additives were investigated. The results show that in the same ratio of raw materials, products synthesized through the two methods have very different selectivity, while additives effect the selectivity of products in Lindsey method,but not in Adler method; the catalyst concentration almost does not affect product selectivity without ethanol, but has a greater impact on products selectivity in ethanol; the reaction time has no effect on product selectivity.3. Combined with the literature and experimental data, the mechanism causing the changes of product selectivity by addition of alcohol was explored. It was found that the ratio of boron trifluoride and alcohol is the key factor affecting the products selectivity.4. In addition, through high-performance liquid chromatography analysis, we investigated the impact of some reaction factors on the relative amount of products synthesized using other mixed-aldehyde and pyrrole as raw materials.As for the Adler method,we investigated the impact of the ratio of raw materials on the relative amount of products synthesized using benzaldehyde, p-chlorobenzaldehyde and pyrrole as raw materials. As for the Lindsey method, we investigated the impact of the addition of ethanol additives on the relative amount of products synthesized using other mixed aldehyde and pyrrole as raw materials.