Synthesis of 3-aminoindenes and cis -1-aminoindanes by Zn(OTf) 2 -catalyzed cyclization of o -alkynylbenzaldehydes with tertiary alkyl primary amines.

Using Zn(OTf) 2 as catalyst, a highly regio- and chemo-selective cyclocarboamination of o -alkynylbenzaldehydes with tertiary alkyl primary amines was realized to access 3-aminoindenes with different substitution patterns from previously reported methods. The full reduction of the iminoindenone intermediates affords cis -1-amino-2-arylindanes with excellent diastereoselectivity. Mechanistically, the reaction involves the rearrangement of 1-amino-3-arylidene-isoindolines and isomerization of 1-aminoindenes to 3-aminoindenes.