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Highlights: [•] Tandem Friedel–Crafts reaction of arenes and cinnamaldehydes was investigated. [•] The cascade reaction affords indenes in good yields. [•] The scope, limitation, and mechanism of the tandem reaction were explored. [•] 1-Phenylindenes generated through a tandem reaction. [•] 1,3-Diphenylindenes generated through a complex cascaded reaction. [Copyright &y& Elsevier]

We prepared a brand new molecule in one step for the synthesis of bis-indolylindane-1,3-dione and indan-1,3-diones from the reaction of ninhydrin and 3 substituted/unsubstituted indoles using [Hbim]BF4 ionic liquid in excellent yields. The method was also used for the synthesis of novel indene-1,3(2H)-denies derivatives. [ABSTRACT FROM AUTHOR]

Thermal and photobromination of octahydro-1H-indene and octahydro-1H-4,7-methanoindene were investigated. Three isomeric tetrabromides (1,3,4,7-tetrabromo-2,3,4,5,6,7-hexahydro-1H-indene) were formed along with a smaller amount of tribromoindane and a pentabromide by thermal bromination of octahydro-1H-indene. The thermodynamically most stable isomers were formed. Morover, thermal and photochemical bromination of octahydro-1H-4,7-methanoindene furnished bromides resulting regiospecifically from the allylic bromination of the five-membered ring. Furthermore, the double bond formed as the intermediate functional group was also brominated due to its pyramidalization. The mechanism proposed for the formation of product distribution was discussed. [ABSTRACT FROM AUTHOR]

Acetylene carbonyl compounds ArC≡CCOR (R = H, Me, Ph) form vinyl cations ArC+CHCOR or ArC+＝CHC(OH)+R at the protonation in Bronsted and conjugate Bronsted–Lewis superacids (protic superacids: HSO3F, CF3SO3H, HSO3F–SbF5, CF3SO3H–SbF5, HAlBr4) with a wide range of acidity (Ho∼−11 to −22). The vinyl cations react with arenes Ar’H with the formation of alkenylation products ArAr’C＝CHCOR. On the contrary to protic superacids Lewis acids (AlBr3, AlCl3) activate additionally electrophilic center at carbonyl carbon of the compounds ArC≡CCOR that leads to the formation of substituted indenes in their reactions with arenes. [Copyright &y& Elsevier]

The TfOH-mediated reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-oles (CF3-substituted diaryl propargyl alcohols) with arenes in CH2Cl2 afford 1,3-diaryl-1-CF3-indenes in yields up to 84%. This new process for synthesis of such CF3-indenes is complete at room temperature within one hour. The synthetic potential, scope, and limitations of this reaction were illustrated by more than 70 examples. The proposed reaction mechanism invokes the formation of highly reactive CF3-propargyl cation intermediates that can be trapped at the two mesomeric positions by the intermolecular nucleophilic attack of an arene partner with a subsequent intramolecular ring closure. [ABSTRACT FROM AUTHOR]