INFLUENCE OF THE STERIC HINDRANCE OF ANCILLARY LIGANDS IN Ru-BASED COMPLEXES APPLIED IN METATHESIS OF CINNAMYL ALCOHOL AND CINNAMYL ACETATE

Cinnamyl alcohol (AC) and cinnamyl acetate (ACM) were used as substrates in olefin metathesis reactions catalyzed by RuCl2(PCy3)2(=CHPh), first-generation Grubbs catalyst-G1, and RuCl2(PCy3)(H2IMes)(= CHPh), second-generation Grubbs catalyst-G2. The reactions occurred in the same reaction conditions for both substrates, 50 °C, for 24 h, in the proportions Ru:substrate of 1:1 and 1:10 mol. At the end of each experiment, the reaction mixture was evaluated by GC-MS and NMR of 13C{1H}. The results revealed different products when G1 and G2 are applied in the metathesis of AC, 1,5-diphenyl-2-pentene and stilbene, respectively. When ACM is the substrate, no product is noted with G1 and stilbene was the compound obtained with G2 as catalyst. In this study, we have presented a discussion about the electronic and steric influence of the ancillary ligands in the yield and type of product formed in the catalytic process.

本研究以肉桂醇（cinnamyl alcohol, AC）与乙酸肉桂酯（cinnamyl acetate, ACM）为底物，分别以RuCl₂(PCy₃)₂(=CHPh)（即第一代Grubbs催化剂G1）与RuCl₂(PCy₃)(H₂IMes)(=CHPh)（即第二代Grubbs催化剂G2）为催化剂，开展烯烃复分解反应研究。两组反应采用完全一致的实验条件：反应温度50 ℃，反应时长24 h，钌催化剂与底物的摩尔比分别为1:1与1:10。每轮实验结束后，均通过气相色谱-质谱联用仪（GC-MS）与碳-13{质子去耦}核磁共振谱（¹³C{¹H} NMR）对反应混合物进行表征分析。结果表明，当以AC为底物时，使用G1与G2催化所得产物存在差异，分别为1,5-二苯基-2-戊烯与二苯乙烯；当以ACM为底物时，G1催化未检测到目标产物，而G2催化仅得到二苯乙烯。本研究探讨了辅助配体的电子效应与空间位阻对该催化反应产物收率及产物类型的影响。