Reaction of 2-acetyl-9-bromofluorene with base afforded Z- and E-2,2′-diacetyl-9,9′-bifluorenylidene in a ratio of 30/70. A similar treatment of 2-stearoyl-9-bromofluorene gave the corresponding bifluorenylidene in a Z/E ratio of 90/10. The observed dependency of Z/E ratio on the chain length is attributable not to steric repulsion, but to intra- and/or inter-molecular attractive forces between the side chains.
2-乙酰基-9-溴芴与碱反应得到Z-和E-2,2'-
二乙酰基-9,9'-亚联
芴,比例为30/70。对 2-硬脂酰基-
9-溴芴进行类似处理,得到相应的二亚
芴,Z/E 比为 90/10。观察到的 Z/E 比对链长的依赖性不是归因于空间排斥,而是归因于侧链之间的分子内和/或分子间吸引力。