Metal‐Free, DBU‐Mediated, Microwave‐Assisted Synthesis of Benzo[c]xanthones by Tandem Reactions of Alkynyl‐1,3‐diketones

Abstract A base‐mediated, green, microwave‐assisted efficient preparation of a diverse benzoxanthone library from variety of readily accessible γ‐alkynyl 1,3‐diketones is reported. The synthesis is based on tandem reactions involving intramolecular cyclization, propargyl‐allenyl isomerization, and electrocyclization in one pot. Some of the benzoxanthones are also synthesized by the one‐pot reaction of 1,3‐diketone and alkynyl bromide under basic heating conditions. This transformation also results in the construction of one new C−C bond and one new C−O bond. magnified image