First Stereoselective Inverse Demand [4 + 2] Cycloaddition Reactions of Novel Chiral Allenamides with Heterodienes. Preparation of Highly Functionalized 2-Arylpyranyl Heterocycles
摘要:
The first stereoselective inverse demand [4 + 2] cycloaddition reactions of chiral allenamides with heterodienes are described here. These reactions lead to stereoselective synthesis of highly functionalized pyranyl heterocycles. A mechanistic model is also proposed here based on the stereochemical assignment and comparisons of stereoselectivities obtained from various chiral allenamides.
Efficient preparations of novel ynamides and allenamides
作者:Lin-Li Wei、Jason A. Mulder、Hui Xiong、Craig A. Zificsak、Christopher J. Douglas、Richard P. Hsung
DOI:10.1016/s0040-4020(00)01014-0
日期:2001.1
achiral allenamides, ynamides are prepared from enamides via bromination followed by base-induced elimination of the Z-bromoenamides. These ynamides and allenamides possess improved thermal stability compared to ynamines and allenamines. They can be isolated, purified, and handled with ease, and thus, should be synthetically more useful than traditional ynamines and allenamines.
Studies on a Urea-Directed Stork−Crabtree Hydrogenation. Synthesis of the C1−C9 Subunit of (+)-Zincophorin
作者:Zhenlei Song、Richard P. Hsung、Ting Lu、Andrew G. Lohse
DOI:10.1021/jo7017922
日期:2007.12.1
[GRAPHICS]A detailed account on the stereoselective synthesis of the C1-C9 subunit of (+)-zincophorin is described here. This approach features the first application of a stereoselective inverse electron demand hetero-[4 + 2] cycloaddition of chiral allenamides in natural product synthesis. The C1-C9 subunit matches Cossy's intermediate, thereby constituting a formal total synthesis. In addition, details of an unusual urea-directed Stork-Crabtree hydrogenation observed during these efforts are also disclosed here.