Synthesis of epoxyisoindolo[1,2-a]isoquinolinium salts by an intramolecular [2+4] cycloaddition reaction in 2-allyl-1-furylisoquinolinium halides

We examined the tandem alkylation/[2+4] cycloaddition of 1-(2-furyl)-3,4-dihydroisoquinolines by various allyl halides. It was found that the process occurred through the intermediate formation of 2-allyl-1-furyl-3,4- dihydroisoquinolinium salts with a subsequent intramolecular exo addition of the allyl fragment to the furan ring. The adducts obtained were structural analogs of the isoindolo-[1,2-a]isoquinoline alkaloids jamtine and hirsutine. © 2013 Springer Science+Business Media New York.