BF3 center dot OEt2 catalyzed synthesis of functionalized 9-fluorene-9-ylidene appended quinazolin-4-ones

An efficient method for the construction of the quinazolinone skeleton from the reaction of 9-(phenylethynyl)-9H-fluoren-9-ols with substituted 2-aminobenzamides catalyzed by boron trifluoride is achieved. The scope of the reaction with several 9-(phenylethynyl)-9H-fluoren-9-ols and substituted 2-aminobenzamides have been demonstrated. Repeating the reaction in the presence of NBS afforded 2-(bromo(9H-fluoren-9-ylidene)methyl)-2-phenyl-2,3-dihydroquinazolin 4(1H)one. The structure of representative compounds was established by the single-crystal XRD method. A plausible mechanism for the formation of the title compounds via the allene carbocation intermediate is proposed. The synthetic utility of products thus formed is demonstrated by utilizing Suzuki coupling and propargylation followed by a 'click' reaction.