PdCl<sub>2</sub>/NaI-Catalyzed Homodimeric Coupling-Cyclization Reaction of 2,3-Allenols: An Efficient Synthesis of 4-(1‘,3‘-Dien-2‘-yl)-2,5-dihydrofuran Derivatives
作者:Youqian Deng、Yihua Yu、Shengming Ma
DOI:10.1021/jo702332m
日期:2008.1.1
A PdCl2/NaI-catalyzed homodimeric coupling-cyclizationreaction of 2,3-allenols was observed to provide an efficient route to 4-(1‘,3‘-dien-2‘-yl)-2,5-dihydrofuranderivatives. By using the easily available optically active starting materials, 2,5-dihydrofurans with high enantiopurity may be prepared. A Pd(II)-catalyzed mechanism was also discussed.
Efficient Synthesis of 4-(2‘-Alkenyl)-2,5-dihydrofurans and 5,6-Dihydro-2<i>H</i>-pyrans via the Pd-Catalyzed Cyclizative Coupling Reaction of 2,3- or 3,4-Allenols with Allylic Halides
作者:Shengming Ma、Wenzhong Gao
DOI:10.1021/jo0163997
日期:2002.8.1
In the absence of a base, palladium(II) catalysts, such as PdCl2, PdCl2(CH3CN)(2), Pd(OAc)(2), and [(pi-C3H5)PdCl](2), can catalyze the cyclizative coupling reaction of 2,3- or 3,4-allenols with allylic halides in DMA at room temperature to provide 2,5-dihydrofurans and 5,6-dihydro-2H-pyrans, respectively, in moderate to good yields. Under similar reaction conditions, nonsubstituted 2,3-allenol 1s affords bimolecular cyclizative coupling product 5s as the major product. The scope of the reaction and its mechanism have been studied briefly. On the basis of the experimental results, the transformation was believed to proceed via a divalent palladium-catalyzed pathway.
Efficient synthesis of 4-(2′-alkenyl)-2,5-dihydrofurans via PdCl2-catalyzed coupling–cyclization reaction of 2,3-allenols with allylic halides
作者:Shengming Ma、Wenzhong Gao
DOI:10.1016/s0040-4039(00)01585-9
日期:2000.11
4-(2'-Alkenyl)-2, 5-dihydrofurans can be efficiently synthesized via the PdCl2-catalyzed coupling-cyclization of allylic halides with 2,3-allenols in DMA at rt in moderate to good yields. The regioselectivity is different from that of the Pd(0)-catalyzed coupling-cyclization of organic halides with 2,3-allenols. (C) 2000 Elsevier Science Ltd. All rights reserved.