SUBSTITUENT EFFECTS AT THE ORIGIN OF A FREE-RADICAL 1,2-ARYL MIGRATION AND IN THE RELATED DISPROPORTIONATION REACTION OF 10-HYDRO-9-P-X-PHENYL-9-PHENANTHRYL RADICALS
SUBSTITUENT EFFECTS AT THE ORIGIN OF A FREE-RADICAL 1,2-ARYL MIGRATION AND IN THE RELATED DISPROPORTIONATION REACTION OF 10-HYDRO-9-P-X-PHENYL-9-PHENANTHRYL RADICALS
复制标题
自由基 1,2-芳基迁移起源和 10-氢-9-P-X-苯基-9-菲基自由基的相关歧化反应中的取代基效应
DOI：
10.1002/chin.197720229
复制
发表时间：
1977
期刊：
影响因子：
--
通讯作者：
B. Vittimberga
中科院分区：
文献类型：
--
作者：
R. Goerner;P. N. Cote;B. Vittimberga
一系列 (9-pX-苯基-9-芴基) 乙醛 (5)(X= H、F、Cl、OCH3、SCH3、SOCH3、SO2CH3 和 CH3) 已被合成、表征，并在存在和不存在苄硫醇的情况下脱羰，产生 (9-pX-苯基-9-芴基) 羰基自由基 (U·)。在硫醇存在下，这些自由基重排生成 9, 10-二氢-9-对X-苯基菲 (7) 和 9-对X-苯基菲 (6)，并从硫醇中提取氢生成 9-甲基-9-对X-苯基芴 (8)。这些产物的相对百分比通过 NMR 积分确定，并用于计算相对重排速率常数 (rel &r)。 log rel 6r 和 Hammett 之间存在极好的线性相关性<（p= 0.39，r= 0.988，s=±0.05）。甲硫基取代的化合物在速率增强的方向上表现出强烈的偏差。在不存在硫醇的情况下，发现重排的10-氢-9-对苯基-9-菲基(R·)发生歧化反应，产生唯一产物6和7。这些产物的相对百分比用于计算相对歧化速率常数(rel ku)。对于含硫取代基和不含硫取代基，获得log rel &d 和ffR 或ur0 之间的单独相关性。有证据表明，抽象基团 (R·) 上的取代基对歧化速率具有控制作用。自 1944 年 Urry 和 Kharasch1 首次发现溶液中的自由基碳重排以来，人们一直在研究自由基碳重排。然而，尽管该领域已进行了三十年的研究，但直到不久前，人们对邻位芳基迁移过渡态的性质或取代基对其的影响知之甚少。稳定性。早期工作2* 5 暗示了取代苯基迁移能力的总体顺序：pC^ NCgH*> p-H3CC6H4= ü CeHs> pH: jCOC (;H4· 不幸的是，这些结果是定性的，并且所研究的系统在空间上非常不同，因此从结果比较中得出的结论是高度暂定的。
A series of (9-pX-phenyl-9-fluorenyl) acetaldehydes (5)(X= H, F, Cl, OCH3, SCH3, SOCH3, SO2CH3, and CH3) have been synthesized, characterized, and decarbonylatedin thepresence and absence of benzyl mercaptan to yield (9-pX-phenyl-9-fluorenyl) carbinyl radicals (U·). In the presence of mercaptan, these radicals rearranged to yield 9, 10-dihydro-9-pX-phenylphenanthrenes (7) and 9-pX-phenyl phenanthrenes (6), and abstracted hydrogen from the mercaptanto yield 9-methyl-9-pX-phenylfluorenes (8). The relative percentages of these products were determined by NMR integration, and were used to calculate relative rearrangement rate constants (rel &r). An ex-cellent linear correlation was found between log rel 6r and Hammett’s<(p= 0.39, r= 0.988, s=±0.05). The meth-ylthio substituted compound showed a strong deviation in the direction of rate enhancement. In the absence of mercaptan the rearranged 10-hydro-9-pOi-phenyl-9-phenanthryl radicals (R·) were found to undergo a disproportionation reaction yielding 6 and 7 as the sole products. The relative percentages of these products were used to calculate relative disproportionation rate constants (rel ku)· Separate correlations were obtained between log rel &d and ffR or ur0 for the sulfur-containing substituents and for the non-sulfur-containing substituents. Evidence is presented which indicates that the substituent on the abstracting radical (R·) exerts the controlling influence on the rate of disproportionation.Free-radical carbon rearrangements in solution have been under investigation since their initial discovery by Urry and Kharasch1 in 1944. Yet, in spite of three decades of research in this area, until a short time ago little was known concerning the nature of the transition state for vicinal aryl migration, or the effects of substituentsupon its stability. Early work2* 5 implied a gross order of migratory abilities for substituted phenyl groups: pC^ NCgH*> p-H3CC6H4= ü CeHs> pH: jCOC (; H4· Unfortunately, these results were qualitative, and the systems studied were sufficiently sterically dissimilar to make conclusionsdrawn from comparison of the results highly tentative.