Asymmetric Heck Reaction

Abstract

The asymmetric Heck reaction is a powerful method for the synthesis of both tertiary and quaternary chiral carbon centers, with an enantiomeric excess often greater than 80%, and in some cases much higher (up to 99% ee). A variety of carbocyclic and heterocyclic systems can be constructed, including spirocyclic systems. The scope of the reaction with respect to the product alkene isomerization is somewhat limited by problems of regioselectivity, however, these problems are surmountable, and a new generation of ligands that dissociate more rapidly from the products, might improve both enantio-and regiocontrol. A variety of chiral compounds prepared 5.2 N,N Ligands 5.3 P,P Ligands and Derivatives 5.4 Other Types of Ligands and Diastereoselective Reactions 6 Methodological Developments 7 Summary and Conclusions

Palladium‐Catalyzed Enantioselective Domino Heck–Cyanation Sequence: Development and Application to the Total Synthesis of Esermethole and Physostigmine

“…Potentially, this modification could be useful for large-scale synthesis because 11 is much cheaper and easier to handle than methyl isocyanate. [19] Enantioselective Heck-cyanation process: A number of palladium-catalyzed enantioselective Heck cyclizations and oligA C H T U N G T R E N N U N G ocyclizations have been developed since the seminal contributions of the groups of Shibasaki [20] and Overman, respectively. [21] Whereas examples of enantioselective Heck cyclization-anion capture of resulting p-allyl-Pd II complexes are known, [22] to the best of our knowledge, the corresponding enantioselective Heck cyclization-anion capture of the resulting s-alkyl-Pd II complex is unknown.…”

An Expedient Variant of Heck Reaction of Alkenyl Nonaflates: Homogeneous Ligand‐Free Palladium Catalysis at Room Temperature

“…Ligands at palladium play a different role depending on the application. While the ligation is crucially important for enantioselective variants of the Heck reaction [2] or activation of otherwise unreactive aryl chlorides, [3] it often tends to deteriorate the desired coupling, causes side reactions and deactivates the catalyst, [4] in particular, when aryl iodides are used as substrates.[5] From this standpoint, it is of no surprise that the fastest versions of Heck reaction known so far are described for ligand-free systems containing free halides (Cl À or Br À added as quaternary ammonium salts) which are believed to stabilize Pd(0)-species.[1d]Later on, it was shown that intermediary Pd nanoparticles as colloids are likely to be the true catalytic species in such systems. [6] Owing to the recent advancements in the mechanistic study and design of robust and efficient low Pd-loading systems, [7] the ligand-free Heck reaction became an emerging trend with particular promise for industrial applications.…”

Stereoselective Synthesis of a Pivotal Chiral Intermediate for Natural Salicylic Macrolides

“…NMR spectra were recorded on Varian GEMINI 300 spectrometer with CHCl 3 (7.26 ppm for 5,156.5,141.2,135.3,132.8,129.6,121.8,116.2,110.6,105.3,72.9,66.2,25.6,25.5;IR (neat) 156.6, 141.2, 135.0, 132.3, 129.9, 121.4, 116.3, 110.8, 105.2, 72.8, 67.0, 25.9, 25.8, 25.5, 18.4, -5.19, -5.24 159.7,156.5,141.7,135.9,135.8,134.8,134.7,134.1,133.9,129.4,129.3,128.6,127.4,127.3,121.4,115.8,110.8,105.0,74.7,67.6,72.1,26.0,25.8,25.6,19.4,18.4,IR (neat) 9,156.6,141.5,139.4,136.0,135.9,135.5,134.9,133.9,133.9,129.5,129.4,127.9,127.4,121.5,…”