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[摘要]：o-(Phenylethynyl)phenyllithiums, generated by treatment of o-(phenylethynyl)bromobenzenes with tBuLi, were quenched with N,N-dimethylcarboamides to afford various 2-phenylindenone derivatives in moderate to good yields upon acidic workup. The choice of lithiation reagents was critical. When n-butyllithium was used the yields were reduced. The N-alkyl groups in the carboamides were also important: quenching with N,N-diethylbenzamides also afforded 2,3-diphenylindenones as the sole isolated products, but quenching with N-benzoylpiperidine led to 2-benzoyltolane in good yield. Control experiments revealed that the reactions proceed through a multi-step reaction sequence involving a novel intramolecular transamination to the a-acetylenic carbon of the alkynyl group. The method was applicable to the synthesis of dibenzopentalene derivatives as well as various indenone derivatives. A mechanism for the reaction is discussed. |
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