Tin Powder-Promoted Cascade Condensation/Allylation/Lactamization: Synthesis of Isoindolinones and Pyrazoloisoindol-8-ones

An efficient tin powder-promoted cascade condensation/allylation/lactamization of 2-formylbenzoic acids, hydrazides, and allyl bromides was developed for the synthesis of isoindolinones in good to excellent yields under mild conditions without any other additives or catalysts. Further manipulation of isoindolinones by iodocyclization process afforded the tricyclic tetrahydro-8H-pyrazolo[5,1-a]isoindol-8-one derivatives, which could be converted into more complicated tetracyclic tetrahydro-4H-azirino[1',2':2,3]pyrazolo-[5,1-a]isoindol-4-ones.