NMR spectral and structural studies on some xanthenones and their thiosemicarbazone derivatives: Crystal and molecular structure of 12-(2-chlorophenyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one

A series of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones [1a–9a] were prepared employing a three component one-pot reaction of aryl aldehyde, 2-naphthol and 1,3-cyclohexanedione using BF3·OEt2 as catalyst. Thiosemicarbazone derivatives [1b–5b] were also prepared in the presence of acid catalyst. All the synthesized compounds have been characterized by IR and NMR. The structure of 5b was confirmed by HSQC spectral analysis. Single crystal X-ray structural analysis of 12-(2-chlorophenyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one evidences the envelope and flattened-boat conformations of cyclohexenone and pyran rings respectively.