Seven 3-methylidene-1H-indol-2(3H)-ones related to the multiple-receptor tyrosine kinase inhibitor sunitinib

Acta Cryst. (2010). C66, o71–o78 (doi.org/10.1107/S0108270109054134)

The structural features of the compounds presented in the solid state correlate strongly with those found in solution. For example, stereoisomer characterisation [(E)- or (Z)-] and the presence of intramolecular hydrogen bonding are confirmed by both techniques although the X-ray study reveals extended intermolecular hydrogen bonding, which is not observed in solution-based techniques (¹H NMR). The predominant motif in the crystal structures is that of intermolecular hydrogen bonding (N–H…O=C) between the 1H-indol-2(3H)-one units. This motif is maintained in the one structure that contains a hydrogen-bonding hydrate molecule. However, one structure, methyl 3-(1-methylethylidene)-2-oxo-2,3-dihydro-1H-indole-1-carboxylate, a carbamate analogue lacking an N–H bond, displays no intermolecular hydrogen bonding.