Highly Stereoselective Iodolactonization of 4,5-Allenoic Acids-An Efficient Synthesis of 5-(1′-Iodo-1′(<i>Z</i>)-alkenyl)-4,5-dihydro-2(3<i>H</i>)-furanones
作者:Xinpeng Jiang、Chunling Fu、Shengming Ma
DOI:10.1002/chem.200801363
日期:2008.10.29
In this paper, it is reported that the efficientiodolactonization of 4,5-allenoic acid with I2 in cyclohexane in the presence or absence of K2CO3 afforded 5-(1'-iodo-1'(Z)-alkenyl)-4,5-dihydro-2(3H)-furanoneshighlystereoselectively. However, the reaction of axially optically active 4,5-allenoic acids (R)-(-)-5 a and (R)-(-)-5 b with I2 afforded the corresponding products with a serious loss of chirality
Studies on Pd<sup>0</sup>-Catalyzed Cyclization of<i>N</i>-3,4-Alkadienyl Toluenesulfonamides with Organic Halides: Selective Synthesis of 2,3-Dihydropyrroles, 1,2,3,6-Tetrahydropyrridines, and Azetidines
作者:Shengming Ma、Fei Yu、Jing Li、Wenzhong Gao
DOI:10.1002/chem.200600431
日期:2007.1
The palladium-catalyzed coupling-cyclization of beta-amino allenes with organic halides ranging from arylhalide to 1-alkenyl halide was studied. 2,3-Dihydro-1H-pyrroles were obtained by reaction of 3-substituted-5-unsubstituted-3,4-allenyl amides under conditions A, while the reaction of 5-substituted-3,4-allenyl amides afforded 1,2,5,6-tetrahydropyridines and/or azetidines with high de under conditions
Highly Regio- and Stereoselective Synthesis of 2(<i>E</i>),4-Alkadienoates via the Pd(0)-Catalyzed Reaction of Aryl Halides with 3,4-Alkadienoates
作者:Chunling Fu、Shengming Ma
DOI:10.1021/ol0473389
日期:2005.4.1
2(E),4-Alkadienoates were prepared highly stereoselectively via the Pd(O)/Ag2CO3-cocatalyzed reaction of 3,4-alkadienoates and aryl halides. The reaction is believed to proceed via the oxidative addition-carbopalladation-,beta-H elimination process. Compared to the other reported methods for the synthesis of 2,4-alkadienoates, in which usually only disubstituted C=C bonds were formed, the current reaction forms the trisubstituted or even tetrasubstituted C=C bond highly stereoselectively.
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.
A palladium catalyzed efficient synthesis of γ-methylene-α,β-unsaturated γ-lactones via cyclization of 3,4-alkadienoic acids
作者:Shengming Ma、Fei Yu
DOI:10.1016/j.tet.2005.06.063
日期:2005.10
An efficient method was developed for the synthesis of gamma-methylene-alpha, beta-unsaturated gamma-lactones from the Pd-catalyzed cyclization of 3,4-alkadienoic acids. Control experiment shows that the reaction should be carried out under a N-2 atmosphere to ensure the high purity of the products. (c) 2005 Elsevier Ltd. All rights reserved.