Iron(III) Chloride‐Catalyzed Tandem Aza‐Prins/Friedel—Crafts Cyclization of 2‐Arylethyl‐2,3‐butadienyl Tosylamides and Aldehydes — An Efficient Synthesis of Benzo[f]isoquinolines.

An efficient approach for the synthesis of 1,2,3,4,5,6-hexahydrobenzo[f]isoquinolines via a tandem aza-Prins/Friedel–Crafts cyclization from 2-arylethyl-2,3-butadienyl tosylamides and aldehydes has been developed. This iron(III) chloride-catalyzed cascade cyclization at the room temperature with different types of aldehydes, such as aromatic and heteroaromatic aldehydes, alkyl aldehydes, and α,β-unsaturated aldehydes, affords the products in moderate to excellent yields (up to 97 %). In this reaction, chlorotrimethylsilane was applied to activate the aldehydes. The cheap catalyst, the mild reaction conditions, and the broad scope of the substrates make this method highly useful.