Conformation and Crystal Structure of Dipyrrinones with Oxindole Components
摘要:
Pyrrole alpha-aldehydes (2-formyl-4,5-dimethyl-1H-pyrrole and 2-formyl-N-methylpyrrole) condense readily at C(3) of indolin-2-ones to give dipyrrinone analogs, such as (3Z)-[(4,5-dimethyl-pyrrol-2-yl)-methylidenyl]-indolin-2-one and (3E)-[(1-methylpyrrol-2-yl)-methylidenyl]-indolin-2one. H-1-NMR NOE analyses and X-ray crystallography confirm the syn-(Z) configuration for the former and the syn-(E) configuration for the latter. The former is stabilized by intramolecular hydrogen bonding. Molecular mechanics calculations of the latter indicate no energy difference between the syn and anti conformations.