Syntheses and Properties of Extremely Stable Di(1-azulenyl)phenylmethyl and (1-Azulenyl)diphenylmethyl Cations Having Dimethylamino Substituents on Their Phenyl Groups
摘要:
一系列极其稳定的二(1-氮烯基)苯基甲基和(1-氮烯基)二苯基甲基阳离子,其苯基上具有二甲基氨基取代基,即通过从相应氢化物中抽取氢化物,合成了二(1-氮烯基)[4-(二甲基氨基)苯基]甲基(5a)和(1-氮烯基)双[4-(二甲基氨基)苯基]甲基(6a)阳离子及其 3-甲基-1-氮烯基(5b 和 6b)和 3,6-二叔丁基-1-氮烯基(5c 和 6c)同系物。对它们的性质进行了全面鉴定。正如预期的那样,这些阳离子的 pKR+ 值随着其苯基上的二甲基氨基取代基的增加而急剧增加。5a-c (pKR+ 13.2-13.8)和 6a-c(pKR+ 12.6-13.3)的值分别比相应的苯基和二苯基甲基阳离子高出 1.4-2.7 和 8.7-9.6 pK 单位。每个阳离子的氧化还原行为也受到取代基的影响。5a-c 在乙腈中的氧化表现出一个几乎不分离的两级氧化波,循环伏安法(CV)显示的电位范围为 +0.75 - +0.87 V 和 +0.89 - +1.01 V vs. Ag/Ag+,这在三(1-氮烯基)甲基阳离子的氧化中也会出现。该波形是由于两个氮烯环被氧化而生成三价物种。6a-c 的氧化反应也在 +0.74 - +0.92 V 的狭窄电位范围内出现了两个波。虽然 6a-c 的还原反应在 -0.94 V 出现了一个不可逆波,但 5a-c 的还原反应在 CV 时在 -0.87 -0.95 V 出现了一个可逆波。我们还研究了 5b 和 6b 随温度变化的 1H NMR 光谱,以弄清它们的立体化学结构。低温核磁共振研究观察到,除了三个芳香环的螺旋桨构象外,金字塔形的二甲基氨基取代基也导致了立体异构化。在较高温度下,核磁共振反映了这些立体异构体的快速异构化。
6-[4-(dimethylamino)phenyl]fulvene (3) and 6-(julolidin-9-yl)fulvene (4) with a set of benzhydrylium ions (reference electrophiles) have been investigated in MeCN. The second-order rate constants for these reactions correlate linearly with the electrophilicity parameters (E) of the benzhydrylium ions. According to the linear free-enthalpy relationship log k2(20 °C) = s(N + E), the nucleophilicity parameters N and
Syntheses and Properties of Extremely Stable Di(1-azulenyl)phenylmethyl and (1-Azulenyl)diphenylmethyl Cations Having Dimethylamino Substituents on Their Phenyl Groups
A series of extremely stable di(1-azulenyl)phenylmethyl and (1-azulenyl)diphenylmethyl cations having dimethylamino substituents on their phenyl groups, i.e., di(1-azulenyl)[4-(dimethylamino)phenyl]methyl (5a) and (1-azulenyl)bis[4-(dimethylamino)phenyl]methyl (6a) cations and their 3-methyl-1-azulenyl (5b and 6b) and 3,6-di-t-butyl-1-azulenyl (5c and 6c) homologs, were synthesized by hydride abstraction from the corresponding hydrides. Their properties were fully characterized. As expected, the pKR+ values of these cations dramatically increased with the dimethylamino substituents on their phenyl groups. The values of 5a—c (pKR+ 13.2—13.8) and 6a—c (pKR+ 12.6—13.3) are higher by 1.4—2.7 and 8.7—9.6 pK units than those of the corresponding analogous phenyl- and diphenylmethyl cations. The redox behavior of each cation was also affected by the substituents. The oxidation of 5a—c in acetonitrile exhibited a barely separated two-step oxidation wave at potential ranges of +0.75 — +0.87 and +0.89 — +1.01 V vs. Ag/Ag+ upon cyclic voltammetry (CV), as occurs in the oxidation of tri(1-azulenyl)methyl cations. The wave is ascribed to the oxidation of the two azulene rings to generate a trication species. The oxidation of 6a—c also showed two waves at a narrow potential range at +0.74 — +0.92 V. Although the reduction of 6a—c exhibited an irreversible wave at −0.94 V, that of 5a—c showed a reversible wave at −0.87 — −0.95 V upon CV. The temperature-dependent 1H NMR spectra of 5b and 6b were also examined to clarify their stereochemistries. Stereoisomerizations due to the pyramidal dimethylamino substituents in addition to the propeller conformations of three aromatic rings were observed by low-temperature NMR studies. At higher temperature the NMR reflects the rapid isomerization of these stereoisomerisms.
一系列极其稳定的二(1-氮烯基)苯基甲基和(1-氮烯基)二苯基甲基阳离子,其苯基上具有二甲基氨基取代基,即通过从相应氢化物中抽取氢化物,合成了二(1-氮烯基)[4-(二甲基氨基)苯基]甲基(5a)和(1-氮烯基)双[4-(二甲基氨基)苯基]甲基(6a)阳离子及其 3-甲基-1-氮烯基(5b 和 6b)和 3,6-二叔丁基-1-氮烯基(5c 和 6c)同系物。对它们的性质进行了全面鉴定。正如预期的那样,这些阳离子的 pKR+ 值随着其苯基上的二甲基氨基取代基的增加而急剧增加。5a-c (pKR+ 13.2-13.8)和 6a-c(pKR+ 12.6-13.3)的值分别比相应的苯基和二苯基甲基阳离子高出 1.4-2.7 和 8.7-9.6 pK 单位。每个阳离子的氧化还原行为也受到取代基的影响。5a-c 在乙腈中的氧化表现出一个几乎不分离的两级氧化波,循环伏安法(CV)显示的电位范围为 +0.75 - +0.87 V 和 +0.89 - +1.01 V vs. Ag/Ag+,这在三(1-氮烯基)甲基阳离子的氧化中也会出现。该波形是由于两个氮烯环被氧化而生成三价物种。6a-c 的氧化反应也在 +0.74 - +0.92 V 的狭窄电位范围内出现了两个波。虽然 6a-c 的还原反应在 -0.94 V 出现了一个不可逆波,但 5a-c 的还原反应在 CV 时在 -0.87 -0.95 V 出现了一个可逆波。我们还研究了 5b 和 6b 随温度变化的 1H NMR 光谱,以弄清它们的立体化学结构。低温核磁共振研究观察到,除了三个芳香环的螺旋桨构象外,金字塔形的二甲基氨基取代基也导致了立体异构化。在较高温度下,核磁共振反映了这些立体异构体的快速异构化。