Banide Emilie V, Ortin Yannick, Seward Corey M, Harrington Laura E, Müller-Bunz Helge, McGlinchey Michael J
UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
Chemistry. 2006 Apr 12;12(12):3275-86. doi: 10.1002/chem.200501169.
1-Phenyl-3,3-biphenyleneallene (2), the base-catalyzed rearrangement product of 9-phenylethynylfluorene (1) yields a yellow, head-to-tail dimer 6 that, upon gentle warming, is converted to the red tail-to-tail isomer trans-3,4-diphenyl-1,2-bis(fluorenylidene)cyclobutane (7), in which the two fluorenylidene moieties severely overlap. The helical sense of the fluorenylidene moieties in 7 matches that of the phenyl substituents, and the interplanar angle between the fluorenylidene moieties is 41 degrees . At 80 degrees C, 6 isomerizes to orange cis-3,4-diphenyl-1,2-bis(fluorenylidene)cyclobutane (8), which at 110 degrees C is converted to orange trans diastereomer 9, whereby the helicity of the overlapping fluorenylidene moieties is reversed from that in 7 such that they are aligned with the ring hydrogen atoms, and the interplanar angle between the fluorenylidene moieties is now 60 degrees . At 180 degrees C, 6 rearranges to dispirodihydrotetracene 3 and blue, electroluminescent diindenotetracene 4, which is readily oxidized to peroxide 5. In the solid state, both 3 and 4 adopt structures with Ci symmetry (only an inversion center) such that the central polycyclic framework is nonplanar. Deprotonation of yellow head-to-tail allene dimer 6 with tBuOK in DMSO and reprotonation with HOAc yields the [1,3]-hydrogen migration product 10, in which the proton originally on the cyclobutane ring is now sited at C9 on the exocyclic fluorenyl substituent. Analogously, deprotonation and reprotonation of orange dimer 9 furnishes [1,3]-hydrogen migration product 11. Side product 17, formed during the synthesis of 1 from 9-phenylethynylfluoren-9-ol, BF3 and Et3SiH, was shown to be a silyl-indene spiro-linked to C9 of fluorene. All products were characterized by NMR spectroscopy and X-ray crystallography, and the mechanisms of these interconversions are discussed.
1-苯基-3,3-联亚苯基丙二烯（2）是9-苯基乙炔基芴（1）的碱催化重排产物，它生成一种黄色的头对头二聚体6，该二聚体在温和加热时会转化为红色的尾对尾异构体反式-3,4-二苯基-1,2-双（芴叉基）环丁烷（7），其中两个芴叉基部分严重重叠。7中芴叉基部分的螺旋方向与苯基取代基的螺旋方向匹配，芴叉基部分之间的面间角为41度。在80℃时，6异构化为橙色的顺式-3,4-二苯基-1,2-双（芴叉基）环丁烷（8），该异构体在110℃时转化为橙色的反式非对映异构体9，由此重叠的芴叉基部分的螺旋性与7中的相反，使得它们与环上的氢原子对齐，芴叉基部分之间的面间角现在为60度。在180℃时，6重排为双螺二氢四并苯3和蓝色的电致发光二茚并四并苯4，4很容易被氧化为过氧化物5。在固态下，3和4都采用具有Ci对称性（仅一个反演中心）的结构，使得中心多环骨架是非平面的。在二甲基亚砜中用叔丁醇钾使黄色的头对头丙二烯二聚体6去质子化，并用乙酸进行再质子化，得到[1,3]-氢迁移产物10，其中原来在环丁烷环上的质子现在位于环外芴基取代基的C9位。类似地，橙色二聚体9的去质子化和再质子化得到[1,3]-氢迁移产物11。在由9-苯基乙炔基芴-9-醇、三氟化硼和三乙基硅烷合成1的过程中形成的副产物17被证明是一个与芴的C9位螺连的甲硅烷基茚。所有产物均通过核磁共振光谱和X射线晶体学进行了表征，并对这些相互转化的机理进行了讨论。
