取代苯甲醛的取代基在硝基苄基鏻参与的Wittig反应中对二苯乙烯分子构型的影响

用硝基苄基鏻与取代苯甲醛经Wittig反应合成了一系列含硝基的二苯乙烯型化合物.研究表明,用硝基苄基鏻在二氯甲烷中进行这类Wittig反应时,随着苯甲醛的取代基不同,得到二苯乙烯主要产物的构型不同,取代基为NMe2,OMe,Me,Cl,H等时主要得到E式产物,取代基为CN和NO2等时主要得到Z式产物;进一步比较3种苄基鏻原料分别与6种不同取代苯甲醛反应后产物的Z/E比,发现用含硝基的苄基鏻作原料时,随苯甲醛上取代基的吸电子效应减小,产物的Z/E比也减小,而用苄基鏻或对甲基苄基鏻作原料时,没有观察到这种Z/E比减小的趋势.通过测定产物的晶体结构,确证了6个目标化合物的分子构型,另外通过核磁共振谱、气-质联用色谱、紫外光谱和红外光谱对各二苯乙烯化合物的结构进行了详细表征.

Effect of Substituents on the Configuration of Stilbene Derivatives in Wittig Reaction of Substituted Benzaldehyde with Nitro-benzyltriphenylphosphonium Salt

A series of nitro-containing stilbene derivatives were synthesized by Wittig reaction of substi-tuted benzaldehyde with nitro-benzyltriphenylphosphonium salt. It was observed that the configuration of the stilbene derivatives depended on the substituents of the substituted benzaldehyde, when the Wittig reac-tions were carried out in CH_2Cl_2. The main products are the E-stilbene for the substituents NMe_2, OMe, Me, Cl and H, but the Z-stilbene for the substituents CN and NO_2. Furthermore the comparison of the Z/E ratio in the reactions of three benzyltriphenylphosphonium salts with six substituted benzaldehydes was made. The results showed that the Z/E ratio of stilbene products diminished as the substituent electron withdrawing ef-fect of group Y in the benzaldehyde decreased in the reaction ofp-NO_2C_6H_4CH_2P~+Ph_3 with YC_6H_4CHO, while the above Z/E change trend was not observed in the reactions of PhCH_2P~+Ph_3, p-MeC_6H_4CH_2P~+Ph_3 with YC_6H_4CHO, respectively. The molecular configuration of the target compounds was identified through the determination of their crystal structures, and their structures were also deliberately characterized by ~1H NMR, GC-MS, IR and UV-Vis techniques.