Kobayashi Kenji, Kitagawa Ryosuke, Yamada Yoshifumi, Yamanaka Masamichi, Suematsu Takako, Sei Yoshihisa, Yamaguchi Kentaro
Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
J Org Chem. 2007 Apr 27;72(9):3242-6. doi: 10.1021/jo062563k. Epub 2007 Mar 31.
Tetrakis(4-hydroxyphenyl)-cavitand 1 and tetra(4-pyridyl)-cavitand 2 self-assemble into a heterodimeric capsule 1.2 via four ArOH...pyridyl hydrogen bonds in CDCl3. The 1.2 expresses the orientational isomerism of an encapsulated unsymmetrical guest with high orientational selectivity because the electronic environment of the 1 unit is different from that of the 2 unit. For p-ethoxyiodobenzene and 2-iodo-6-methoxynaphthalene encapsulated in 1.2, the iodo group is specifically oriented to the cavity of the 2 unit. The orientational isomeric selectivity for methyl p-acetoxybenzoate and methyl p-ethoxybenzoate within 1.2 is 1:0.11 and 1:<0.05, respectively, wherein the methyl ester group is preferentially oriented to the cavity of the 2 unit. The delicate balance among electrostatic potential repulsion, CH-pi interaction, or CH-halogen (halogen-pi) interaction, in 1.2-guest assembly influences the orientational isomeric selectivity of unsymmetrical guests within 1.2.
四（4-羟基苯基）穴番1和四（4-吡啶基）穴番2在CDCl₃中通过四个ArOH…吡啶基氢键自组装成异二聚体胶囊1.2。1.2表现出对包封的不对称客体具有高取向选择性的取向异构现象，因为1单元的电子环境与2单元不同。对于包封在1.2中的对乙氧基碘苯和2-碘-6-甲氧基萘，碘基团特异性地朝向2单元的空腔。1.2中对甲基对乙酰氧基苯甲酸酯和甲基对乙氧基苯甲酸酯的取向异构选择性分别为1:0.11和1:<0.05，其中甲酯基团优先朝向2单元的空腔。1.2-客体组装中静电势排斥、CH-π相互作用或CH-卤素（卤素-π）相互作用之间的微妙平衡影响了1.2中不对称客体的取向异构选择性。
