Reliable transformation of substituted 2-aminobenzophenones into methoxy substituted 9H-xanthene-9-ones and/or fluoren-9-ones

An easy conversion of substituted 2-aminobenzophenones to some novel 9H-xanthene-9-ones and/or fluoren-9-ones is reported. Potassium chromate oxidation of 2-nitrobiphenyl methanol afforded 2-nitrobenzophenone derivatives that were reduced to give the substituted 2-aminobenzophenones. Cyclization of substituted 2-aminobenzophenones with n-amylnitrite and potassium iodide by stirring at r.t for 12 h delivered methoxy substituted 9H-xanthene-9-ones in 73–96% yields. Reaction of aminobenzophenone with n-amylnitrite leads to a mixture of 9H-xanthene-9-ones and fluoren-9-ones. Optimization of the reaction time and the reagents on the synthesis of 9H-xanthene-9-ones and fluoren-9-ones is presented as well. The synthesized structures have been elucidated unambiguously by (1H/13C NMR), Heteronuclear Single Quantum Spectroscopy (HSQC) and Heteronuclear Multiple-Bond Spectroscopy (HMBC) spectra.

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