1,3-偶极环加成反应合成1-(取代苄基)-1,2,3-三唑类化合物

Synthesis of 1-(Substituted benzyl)-1,2,3-triazoles by 1,3-Dipolar Cycloaddition Reaction

利用苄氯和取代苄氯与叠氮化钠的亲核取代反应合成了一系列苯环上带有不同取代基团的苄基叠氮化合物 ,亲核取代反应速率受苯环上取代基的影响 :吸电子基团的存在 ,可以促使反应更容易进行 .合成的叠氮化合物与苯乙炔经 1,3 偶极环加成反应得到了相应的取代苄基 1,2 ,3 三唑类化合物 ,反应条件温和 .这些 1,2 ,3 三唑类目标化合物具有对热稳定的优点 .用红外、核磁、元素分析、质谱等对合成的叠氮化合物和 1,2 ,3 三唑类化合物的结构进行了表征 ,重点研究了 1,3 环加成反应的规律 .加成反应速率取决于叠氮化合物 (偶极物 )的极性 ,即与取代基的电负性有关 :苯乙炔 (亲偶极物 )易于与缺电子的叠氮反应 ,反之亦然 .同时在反应过程中观察到空间位阻效应 :反应可以生成两种同分异构体 ,其中 4 苯基 1,2 ,3

Benzyl azide, 4-methyl-benzyl azide, 4-cyano-benzyl azide, 4-fluoro-benzyl azide and 1,1'-biazidomethyl-4,4'-biphenyl were prepared by the nucleophilic substitution reaction of NaN3 with substituted benzyl chlorides. The reaction rate was affected by the substitution groups at the phenyl ring, and electron-withdrawing groups could accelerate the rate. And 1,3-dipolar cycloaddition reaction of the azides with phenylacetylene was studied. The corresponding compounds (azides and 1,2,3-triazoles) were characterized with NMR, FT-IR and elementary analysis. The 1,2,3-triazoles were thermal stable. The addition rate depended on the substitution groups of the azides (1,3-dipole), and the reactivities correlated with polar effects: phenyacetylene (dipolarophile) reacted faster with electron-poor azides and vice versa. The 1, 3-dipolar cycloaddition reaction was found to be regioselective, and the 4-phenyl-1,2,3-triazoles were the major products in the two structural isomers of 1,2,3-triazoles obtained.