Opposite π-Face Selectivity for the DMD and m-CPBA Epoxidations of Chiral 2,2-Dimethyloxazolidine Derivatives of Tiglic Amides: Control by Steric Interactions versus Hydrogen Bonding
摘要:
A high extent but opposite sense in the diastereoselectivity has been observed for the DMD and m-CPBA epoxidations of the optically active tiglic amides (S)-1 with 2,2-dimethyloxazolidines as chiral auxiliaries, This unprecedented reversed pi-facial differentiation for these two peroxidic oxidants is rationalized in terms of like (lk) and unlike (ul) transition structures: For DMD, steric interactions dominate, such that the unlike transition structure is favored, while for m-CPBA, hydrogen bonding effects overcome these steric repulsions and the like one is preferred.
Rh<sup>III</sup>‐Catalyzed Oxidative Olefination of Vinylic CH Bonds: Efficient and Selective Access to Di‐unsaturated α‐Amino Acid Derivatives and Other Linear 1,3‐Butadienes
作者:Tatiana Besset、Nadine Kuhl、Frederic W. Patureau、Frank Glorius
DOI:10.1002/chem.201101340
日期:2011.6.20
get‐together! A RhIII‐catalyzedoxidative cross‐coupling of different olefins was developed, resulting in the formation of valuable linear butadiene products and especially di‐unsaturated α‐amino acid derivatives. 1,1‐Di‐, 1,2‐di‐, and 1,1,2‐trisubstituted olefins could be coupled with styrenes and acrylates. In these reactions, remarkably high levels of chemo‐, regio‐, and stereoselectivity were obtained