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No simple way has yet been reported for preparing fluoranthene derivatives containing alkyl or aryl groups in which the position of the substituent is known. Most syntheses of fluoranthenes so far described (1, 2) require several steps. It has been found that the most suitable procedure is that of Dilthey (2) who treated acecyclone (III; R, R' = C-gH5) with maleic anhydride, and obtained the anhydride of 7,10-diphenylfluoranthene-8,9-dicarboxylic acid. Extension and modification of this procedure has led to the formation of a large number of new substituted fluoranthenes (VI), in which all the substituent groups are in the left-hand ring.The starting material is acenaphthenequinone, which is condensed with various alkyl ketones at 25-30°in methanol with an alkaline catalyst. As with benzil (3), three types of products result. Methyl n-alkyl ketones, in general, give carbinols (I) which, upon dehydration, do not give substituted cyclopentadienones but non-reversible dimers. Other ketones, however, give carbinols which may be dehydrated to a reversible dimer (II) or the corresponding monomeric cyclopentadienone (III). In some instances, the carbinol is unstable, even at 25-50°under the conditions of the condensation, so that the dienone results directly. The carbinols that are stable at room temperatures may also be converted to the cyclopentadienone by refluxing in alkaline solution. All these points of behavior were noted in our previous paper on simple substances (3).The structure of the dimer (II) has not been proved, but is written as shown

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