Enantioselective synthesis of azepine-fused planar-chiral ferrocenes was achieved by the chiral cationic Pt-catalyzed intramolecular cycloisomerization of N-propargyl-2-ferrocenylanilines. A mechanistic study using an N-allenyl analogue indicated that the reaction proceeded selectively in a 7-exo-dig manner along with isomerization of the exo-olefin moiety. A methanesulfonylamino tether was crucial for selective cycloisomerization. This is the first example of the enantioselective synthesis of heteropin-fused planar-chiral ferrocenes.
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