PdCl₂-Catalyzed Two-Component Cross-Coupling Cyclization of 2,3-Allenoic Acids with 2,3-Allenols. An Efficient Synthesis of 4-(1‘,3‘-Dien-2‘-yl)-2(5H)-furanone Derivatives

Cross-coupling cyclization reaction between 2,3-allenoic acids 1 and 2,3-allenols 2, in which two allenes functioned differently, was realized to afford 4-(1‘,3‘-dien-2‘-yl)-2(5H)-furanone derivatives 3. The reaction may proceed via an oxypalladation, insertion, and β-hydroxide elimination process. A high E-stereoselectivity of the new formed CC double bond was observed.