1,1-Di(9-fluorenyl)ethyl acetate, a by-product from the acetylation of 9-fluorenyllithium.

The preparation of sp-9-acetylfluorene from the reaction of 9-fluorenyllithium with acetyl chloride also provided 9-(1-acetoxyethylidene)fluorene ('diacetylfluorene') and 1,1-di(9-fluorenyl)ethanol, (II), as by-products recently characterized by X-ray analysis. A third by-product, 1,1-di(9-fluorenyl)ethyl acetate, (III), C(30)H(24)O(2), has now been unequivocally identified for the first time, and emanates from the acetylation of the oxyanion of (II). In the asymmetric unit, compound (III) exists as two almost identical structures which differ slightly, but significantly, in conformation. Neither possesses the significant fluorene-ring bowing or the perpendicularity of the two ring planes exhibited by (II). The angle between the least-squares planes of the two fluorene rings of (III) is 58.45 (9) and 60.95 (10) degrees, respectively, for the two conformations, and their corresponding bonding parameters also differ slightly in a number of instances.