相转移催化反应研究 V.利用^(14)C标记法研究取代苯乙烯及α-芳代苯乙烯与二溴卡宾反应动力学

Studies on Phase Transfer Catalysis Ⅴ. A Kinetic Study of the Cycloaddition of Dibromocarbene with Substituted Styrenes and α-Arylstyrenes by ^(14)C Labelling Method

本文应用放射性计数进行反应物及产物的定量测定,比较了一些冠醚类相转移催化剂的性能.发现新型氮杂冠醚在催化二溴卡宾与1,1-二苯乙烯加成反应时有最好的催化性能.

The relative rate constants krel of the PTC reaction of p-substituted styrene(1a-1e)with dibromocarbene were measured by radiocounting method and the krel values were analyzed by lineal correlation method according to Brown’s formula(lgkrel=lgk0+ρ+σ+).It was found thatρ+value obtained this way was identical to the results of GC method reported in our early paper.Theρ+value of the PTC reaction ofα-arylstyrene(1f-1k)with dibromocarbene system was smaller than the one obtained from substituted styrene reaction.It was suggested that the aryl group ofα-arylstyrene might disperse the positive charge fromαcarbom atom.A variety of the crown compounds were used as PTC catalysts for the reaction of 1,1-diphenylethylene and dibromocarbene and it was found that N,N’-di-substituted azacrown possessed the highest catalytic activity for this reaction.Six 1-14C-1,1-dibromo-2-aryl-2-phenyl-cyclopropanes were prepared and identified by comparison with the unlabelled authentic samples(2f-2k)which were characterized by elemental analysis,NMR,MS,and TLC analysis.