Molecular diversity of the cyclization reaction of 3-methyleneoxindoles with 2-(3,4-dihydronaphthalen-1(2H)-ylidene)malononitriles

Abstract

The cyclization reaction of 3-methyleneoxindoles with 2-(3,4-dihydronaphthalen-1(2H)-ylidene)malononitrile in ethanol in the presence of DBU at room temperature afforded functionalized 3′-iminospiro[indoline-3,2′-phenanthrenes] in good yields. However, the similar reaction of ethyl 2-cyano-2-(3,4-dihydronaphthalen-1(2H)-ylidene)acetate resulted in functionalized 3-oxospiro[indoline-3,2′-phenanthrenes] and benzo[d]phenanthro[2,3-f][1,3]diazepines depending on the structures of substrates. Furthermore, the cycloaddition reaction of 3-phenacylideneoxindole with ethyl 2-cyano-2-(3,4-dihydronaphthalen-1(2H)-ylidene)acetate produced the spiro[indoline-3,2′-phenanthrene]-4′-carbonitrile derivatives. The stereochemistry of the cyclic spirooxindoles was clearly elucidated by ¹H NMR data and fourteen single crystal structures.