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(5<i>H</i>)-furanone Derivatives

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