BF3•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.

Automated summary

An efficient method for constructing the quinazolinone skeleton has been achieved by catalyzing the reaction between 9-(phenylethynyl)-9H-fluoren-9-ols and substituted 2-aminobenzamides using boron trifluoride. The scope of this reaction has been demonstrated using various substrates. The reaction with NBS produced 2-(bromo(9H-fluoren-9-ylidene)methyl)-2-phenyl-2,3-dihydroquinazolin-4(1H)-one. The synthesized compounds have been structurally characterized and a plausible mechanism for their formation has been proposed. The synthetic utility of the products has been demonstrated through further reactions.