Efficient preparation of the isoindoline framework via a six component, tandem double A3-coupling and [2+2+2] cycloaddition reaction

The preparation of tetrasubstituted isoindolines from three alkyne units, two aldehyde units and a primary amine via three consecutive reactions. two aldehyde-amine-alkyne couplings (A(3)-couplings) and a final [2+2+2] cycloaddition, in a single synthetic operation, is described. The A(3)-couplings are catalyzed by copper bromide and the cycloaddition is catalyzed by Wilkinson's catalyst. It was found that many catalysts known to be efficient at the cycloaddition step were not suitable when this step was part of the tandem reaction sequence. Wilkinson's catalyst was found to be unique in its suitability for the overall domino reaction sequence.