An Indenone Synthesis Involving a New Aminotransfer Reaction and Its Application to Dibenzopentalene Synthesis

作者：Katsumoto Kenta; Kitamura Chitoshi; Kawase Takeshi^*

来源：European Journal of Organic Chemistry, 2011, (25): 4885-4891.

DOI：10.1002/ejoc.201100575

• Cyclization
• Alkynes
• Fused-ring systems
• Aromatic compounds
• Reaction mechanisms

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.

• 出版日期2011-9