Synthesis of cyclopropanes by intramolecular attack of N-nucleophiles on the central carbon of (pi-allyl)palladium complexes

ortho-Halobenzamides such as compound la react in the presence of allene an d base with catalytic amounts of palladium(0) complexes to form cyclopropan es such as 3a. This reaction is believed to proceed via an intermediate pal lada-cyclobutane and is the first example of a noncarbon nucleophile attack on the centre carbon of an (eta (3)-allyl)palladium complex leading, by re ductive elimination, to cyclopropanes. The regiochemistry of the nucleophil ic attack (central versus terminal carbon) depends on the nature of Ligand and solvent as electron rich palladium complexes favour central carbon atta ck.