Exclusive regioselective 1,3-dipolar cycloaddition of 9-diazo-9H-fluorene and diphenyldiazomethane to 2-arylideneindane-1,3-diones: new approach toward effective synthesis of novel spiropyrazole derivatives

Abstract: A simple, convenient, and regioselective 1,3-dipolar cycloaddition of 9-diazo-9H-fluorene or diphenyldiazomethane to 2-arylidene-1H-indene-1,3(2H)-diones afforded a series of novel dispiro[indane-2,3′-pyrazole-5′,9″-fluorene] and spiro[indene-2,3′-pyrazole] derivatives in moderate to excellent yields. Chemical structures of all products have been fully established by 1D (¹H, ¹³C, ¹³C-DEPT 90) and 2D homonuclear and heteronuclear correlation NMR spectrometry experiments (¹H-¹H-DQF-COSY, ¹H-¹H-TOCSY, ¹³C-¹H-HSQC, ¹³C-¹H-HMBC, ¹H-¹H ROESY, and HSQC-TOCSY) and regioselectivity of the reported procedure has been demonstrated in all products. DFT reactivity indices of these cycloaddition reactions have been studied. 1,3-Dipolar cycloaddition of 9-diazo-9H-fluorene and diphenyldiazomethane to 2-arylidene-1H-indene-1,3(2H)-diones as dipolarophiles are reactions governed by a concerted mechanism exhibiting high regioselectivity. Graphical abstract: [Figure not available: see fulltext.].