Photocatalyzed Intramolecular [2+2] Cycloaddition of N ‐Alkyl‐ N‐( 2‐(1‐arylvinyl)aryl)cinnamamides

N ‐Alkyl‐ N‐( 2‐(1‐arylvinyl)aryl)cinnamamides are converted into natural product inspired scaffolds via iridium photocatalyzed intramolecular [2+2] photocycloaddition. The protocol has a broad substrate scope, whilst operating under mild reaction conditions. Tethering four components forming a trisubstituted cyclobutane core builds rapidly high molecular complexity. Our approach allows the design and synthesis of a variety of tetrahydrocyclobuta[ c ]quinolin‐3(1 H )‐ones, in yields ranging between 20–99 %, and with excellent regio‐ and diastereoselectivity. Moreover, it was demonstrated that the intramolecular [2+2]‐cycloaddition of 1,7‐enynes—after fragmentation of the cyclobutane ring—leads to enyne‐metathesis‐like products.