Efficient synthesis of fluorene derivatives via benzannulation of indene dienes with benzoylacetonitrile catalyzed by lipase

In this work, an enzymatic method for the synthesis of fluorene derivatives via benzannulation of indene dienes with benzoylacetonitrile in non-aqueous solvent was developed. Under the optimal reaction condition (indene diene (0.5 mmol), benzoylacetonitrile (0.5 mmol), ethanol (2 mL), lipase from porcine pancreas (5 mg), 50℃, 24 h.), fluorenes bearing different groups were obtained in satisfactory yields (83 %-93 %). This method not only offers a significant advancement in the synthesis of fluorene derivatives , but also mines a new application of lipase in enzyme catalytic promiscuity.