Fluorenes elimination reactions

The results of a thorough study of the kinetics, products and stereochemical course for the nucleophilic substitution and elimination reactions of ring-substituted 9-(l-Y-ethyl)fluorenes ([31]-Y, Y = Br, I, brosylate) have been reported (Scheme 19).121,122. The reactions of the halides [31]-Br and [31]-I were proposed to proceed exclusively by a solvent-promoted ElcB reaction or an E2 reaction with a large component of hydron transfer in the transition state .122... 

Solvolysis of the R,R and R,S isomers of 2-bromo-9-(l-X-ethyl)fluorenes, X = Cl, Br, I, or OBs, in 25% (v/v) acetonitrile in water has been studied with respect to rates of formation of elimination products and of substitution products (X = OH or NHCOMe).142 The parent 9-(l-X-ethyl)fluorenes and the 2,2/-dibromo-9-(l-X-ethyl)-fluorenes were also studied. Various effects of leaving group and of the presence of nucleophiles on the competition between the reactions were observed and the Bronsted equation was applied to the results for the elimination reactions. A related study of solvolysis of 9-(X-methyl)fluorenes, X = I, Br, or Bs, was also carried out, in which the Swain-Scott equation was applied to nucleophilic selectivities in the S 2 reactions.143... 

Reaction HI. Oxidation under certain Conditions of Lower Hydrocarbons. (B., 32, 432.)—In this reaction two molecules of a hydrocarbon are condensed, hydrogen being eliminated by the action of an oxidising agent. Two neutral oxidising agents, potassium persulphate and lead oxide, are especially useful in this type of reaction. The former is used in dilute aqueous solution, at a temperature of about 100° to obtain results with the latter much higher temperatures are necessary. The substance is mixed with the lead oxide and heated to over 250°, or it is distilled over heated lead oxide. The results obtained vary with the temperature and the amount of lead oxide used, e.g., fluorene can be oxidised to either... 

Some PAHs are degraded by oxidation reactions that have been measured in the dark (to eliminate the possibility of photodegradation). Korfmacher et al. (1980) found that, while fluorene was completely oxidized, fluoranthene and phenanthrene were not oxidized, and benzo[a]pyrene and anthracene underwent minimal oxidation. These compounds were tested adsorbed to coal fly ash the authors stated that the form of the compound (adsorbed or pure) and the nature of the adsorbent greatly affected the rate and extent of oxidation. 

Furthermore, the reaction of diphenylacetylene with iodobenzene under Jeffery conditions gave rise to 9-alkylidene-9H-fluorene 178. The reaction is explained by a novel migration of the alkenylpalladium intermediate 179 to the arylpalla-dium species 180. Finally 178 is formed via the palladacycle 181 and reductive elimination [59]. 

The substitution reactions of R2CHP(0)(NMeR )Cl (141 I CH = fluoren-9-yl R = CHMePh) with secondary amines (Mc2NH, EtaNH, Pr NHEt) are largely stereospecific or non-stereospecific depending on the bulk of the amine and its concentration two elimination-addition pathways (Scheme 24), differing in whether... 

Results of a Hammett study of elimination of substituted fluoren-9-ylmethyl ben-zenesulfonate suggest that in NaOMe-MeOH p = 0.74) the reaction proceeds by the E2 mechanism. In contrast, the Hammett plots obtained for reaction promoted by... 

In 2001, Larock and Tian reported a palladium-catalyzed cascade reaction of aryl halides and 1-aryl-l-aIkynes to synthesize 9-aIkylidene-9/f-fluorenes 167 [66] (Scheme 6.44). Based on the active role of Pd(IV) in organopalladium chemistry, the authors proposed a mechanism involving the formation, transformation, and reductive elimination of Pd(IV) intermediates and aryl C—H bond activation. It is noteworthy that both carbocyclic and heterocyclic aryl iodides, such as pyridine and thiophene, could be introduced in this reaction. Later, Zhao and Larock reported an efficient palladium-catalyzed cascade reaction for the synthesis of substituted carbazoles 169 from A/-(3-iodophenyl)anilines 168 and alkynes [67] (Scheme 6.45). 

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