Fig. 4: Synthesis of extended π-systems and synthetic applications.
From: Alkyne–Alkene [2 + 2] cycloaddition based on visible light photocatalysis
Racemates for all cyclobutenes. a Tandem cycloaddition followed by rearrangement of benzofuran and benzothiophenes. (ISC = Intersystem crossing). b Derivatization of coumarin. (DDQ = 2,3-dichloro-5,6-dicyano-1,4-benzoquinone). c Synthesis of exomethylene cyclobutene. d Synthesis of γ-lactam and pyrrolidine derivatives.
