Study On Synthesis Of Trans-stilbenes

(E)-stilbenes, such as resveratrol, Piceatannol, Combretastatin A-1 et al, have taken extensive attention due to their outstanding biological activities and pharmacological properties including anti-inflammatory, antioxidation, platelet antiaggregation, heart protection and anticarcinogenic effects. However, the limited natural resource of (E)-stilbenes has restricted the research about their pharmacological activities and applications.It becomes much more important to search for the synthetic methods for preparation of (E)-stilbenes. Previous research has proved that the synthetic (E)-stilbenes have identical physiological action with that obtained from the natural source.In this thesis, three methods had been developed searching for a facile and highly stereoselective synthetic method for preparation of (E)-stilbenes.The first section is a summary on the biological activity and previous synthetic methods of (E)-stilbenes.In the second section four (E)-4-nitrostilbenes were synthesized in excellent yield by an efficient condensation dehydration of P-nitrotoluene with substituted benzaldehyde in the presence of three kinds of bases and catalysts. The optimal result was given after the various reaction conditions were investigated and the products are conformed by IR, ¹H NMR, ¹³C NMR, and element analysis. Therefore, the condensation reaction is a facile and highly stereoselective synthetic method to (E)-stilbenes.In the third section (E)-1-(4-nitrophenyl)-2-(3,5-dimethoxyphenyl)ethene was reduced by three kinds of systems(Fe-HCl, Zn-CaCl₂, NH₂NH₂H₂O-KOH). (E)-1-(4-aminophenyl)-2-(3,5-dimethoxyphenyl)ethene was obtained in the high yield, and the persistence of configuration was investigated by IR and ¹H NMR.In the fourth section the application to synthesizing (E)-stilbenes of McMurry coupling reaction of aromatic aldehydes was studied. Three kinds of methoxy-substituted (E)-stilbenes were synthesized which has one asymmetric (E)-stilbene. It is found that symmetrical (E)-stilbenes are obtained with a higher selectivity and a good yield by McMurry coupling reaction. However, the products of crossed couplingreaction are complex and the yield is low.In the fifth section the application to synthesizing (E)-stilbenes of Grignard reaction was studied. Firstly, Grignard reagent was prepared by benzyl chloride or />methoxychlorobenzyl. 1,2-Diarylethanol was obtained by the reaction of Grignard reagent and substituted benzaldehyde. (E)-stilbene was obtained by dehydration. In this paper, Grignard reaction under ultrasonic radiation was studied. In comparison with conventional condention, it had no further use for harsh terms such as anhydrous solvent, inert atomosphere. And this paper examined effect of the pattern of substrate addition on Grignard reaction.