PdCI_2-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

摘要

The transition metal-catalyzed coupling cyclization reaction of functionalized allenes with organic halides has caught the attention of many synthetic chemists due to the great potential of allenes as a result of their unique reactivity,axial chirality,and substituent-loading capability.Hashmi et al.reported the homodimerization reaction of 1,2-allenyl ketones.We also have shown strong interest in the reactions involving two allenes by reporting the heterodimer-ization reaction of 2,3-allenoic acids with 1,2-allenyl ketones and homodimerization of 2,3-allenoic acids.It should be noted that in these two reactions (1) the Pd(II) species was regenerated by consuming a large amount of 1,2-allenyl ketones via cyclometa-lation/protonation or an additional oxidant via direct oxidation and (2) both allenes were cyclized.We wish to report here a coupling cyclization protocol of two different allenes,in which (1) the catalytically active Pd(II) species would be regenerated "automatically" after the reaction and (2) two allenes function differently,that is,2,3-allenoic acids form the butenolide skeletons while the 2,3-allenols introduce the 1,3-diene substituent to the beta-position of the butenolides formed.