Nitrogen Configuration Determined by X-ray Analysis on an Homogeneous Series of 3-Indolines

The X-ray diffraction analyses of 2-metbyl-2-phenylindolin-3-one 1, 1,2-dimethyl-2-phenylindolin-3-one 2, 1-hydroxy-2-methyl-2-phenylindolin-3-one 3 and 1-methoxy-2-methyl-2-phenylindolin-3-one 4 have been carried out and the structural data were compared with those of 1-oxyl-2-methyl-2-phenylindolin-3-one 5. The results demonstrate that only compounds 2 and 5 show planar trigonal geometry which is coplanar with the conjugated benzene ring of the indolinic nucleus, whereas compounds 3 and 4 show a marked pyramidality of the nitrogen. Even if compound 1 shows a certain pyramidality of the nitrogen, it has been considered similar to compound 2. The reactivity of all studied compounds fit the structural data.