Dibenzothiophene → 2-Methyl-1,2-dihydrobenzo[b]indeno[4,5-d]thiophen-3-one

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For the synthesis of the compounds according to the invention, the operation started with 2-methyl indan-1-one and, in a three-step method, the desired 2-methyl indene was obtained in a yield of over 60%. As emerges from the diagram, m-xylene (1) is converted in a first step with methacryloyl chloride. The purified indanone (2) is obtained after cleaning by distillation and Friedel-Crafts alkylation in a yield of 66%. The reduction of the indanone (2) is implemented with NaBH4. The indene (3) is obtained as a viscous fluid. By reaction of the compound (4), which is produced by addition of 1,2-dibromoethane and fluorenyl lithium, the two isomers (5) and (6) are obtained in a subsequent reaction in a yield of 45%. The desired isomer 5 can then be isolated by crystallisation from toluene/hexane in a ratio of 1:2.

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