Palladium catalyzed coupling reactions of 2,3-dihydrofuran using high pressure conditions

Hillers, Stephan; Reiser, Oliver

doi:10.1016/s0040-4039(00)73969-4

Cited by 43 publications

(7 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[50] An interesting corollary to this work was reported by Reiser et al, who found that at high pressure the enantiomeric excess of the major product in the conversion of 100 to 102/103 was dramatically increased, suggesting that such conditions enhanced the kinetic resolution process. [51] Shibasaki et al demonstrated that the reaction can be performed using hypervalent alkenyliodonium salts instead of alkenyl triflates (transformation of 111 to 112, Scheme 27), although yields are lower due to the highly reactive nature of the salts, which leads to competition from uncatalyzed and/or non-phosphine mediated processes. [52] In this case, only the 2-alkenyl-2,5-dihydrofuran 112 is obtained, suggesting that dissociation from the Pd complex formed after the first b-hydride elimination is more rapid than when using triflates.…”

Section: Dihydrofurans and Cyclic Enol Ethersmentioning

confidence: 99%

Asymmetric Heck Reaction

2004

View full text Add to dashboard Cite

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

show abstract

Section: Dihydrofurans and Cyclic Enol Ethersmentioning

confidence: 99%

Asymmetric Heck Reaction

2004

View full text Add to dashboard Cite

show abstract

“…In solutions chemical reactions that experience a change in volume as a consequence of either bond breaking or bond formation or of differential solvation will be affected by high pressure. Cycloadditions represented by the Diels‐‐Alder reaction serve as prime examples of the dramatic effect on the rates of reaction that can be observed at high pressure of 7.5 kbar [36,37]. The normally explosive reaction between hydrogen and oxygen is shut down by pressure at ambient temperature.…”

Section: High Pressurementioning

confidence: 99%

The role of water structure in conformational changes of nucleic acids in ambient and high‐pressure conditions

Barciszewski

Jurczak

Porowski

et al. 1999

European Journal of Biochemistry

View full text Add to dashboard Cite

This review describes and summarizes data on the structure and properties of water under normal conditions, at high salt concentration and under high pressure. We correlate the observed conformational changes in nucleic acids with changes in water structure and activity, and suggest a mechanism of conformational transitions of nucleic acids which accounts for changes in the water structure. From the biophysical, biochemical and crystallographic data we conclude that the Z-DNA form can be induced only at low water activity produced by high salt concentrations or high pressure, and accompanied by the stabilizing conjugative effect of the cytidine O4 H electrons of the CG base pairs.Keywords: structure of water, high pressure, conformational changes, nucleic acids.Water molecules influence specific interactions in all biological systems and yet it is still extremely difficult to understand their effect in precise atomic models. Recent studies of water effects on biological macromolecules have made molecular biologists aware of the important role that this solvent plays in the structure and function of proteins, nucleic acids and other cell constituents. Also we now realize how little we know about the detailed behaviour of water molecules. In recent years there has been an explosion in the number of new X-ray structures for protein±DNA complexes and other biomolecules. Many of those structures feature water molecules buried at the intermolecular interface, or assign them with reasonable confidence to good geometry of water oxygen atoms, at the coordination space of hydrogen bond donors and acceptors. Thus, hydrogen bonding networks between proteins and nucleic acids often include water molecules, which have not been anticipated from our previous understanding of the molecular basis for macromolecular recognition, which always predicted direct contacts between functional groups. The contribution of hydration to the energetics of macromolecular assembly and catalysis was recognized a long time ago. The cost of removing all the perturbated water, or the benefit of fully hydrating a newly exposed surface is around 3.6±62.7 kJ´mol 21 per 100 A Ê 2 . It is rather high in comparison to ATP molecule hydrolysis which yields 30.5 kcal´mol 21 .We now put forward several basic questions concerning water interactions with proteins and nucleic acids, the strength of these interactions, and their localisation, structure and effect on the conformation of various biological macromolecules. The role of water in biology is not very well understood in detail and is still controversial. Water molecules appear to be both the cement that fills crevices between amino acid building blocks and the lubricant that allows motion of these elements [1]. In consequence, they allow a biological molecule to adopt a tertiary structure without being trapped in a local minimum energy state, as well as to compensate for a poor steric fit of side chains in macromolecule interiors and substrates in the binding sites [2,3]. These interactions of water mol...

show abstract

“…At atmospheric pressure the two enantiomers were formed with 4.5 % ee, whereas at 500 MPa an increase to 20.4 % ee was observed which corresponds to a A A V = -(1.7 & 0.2) cm3 mol-'. Another example of a pronounced positive pressure effect on enantioselectivity was found by Hillers and Reiser [82] for the Heck reaction of 2,3-dihydrofuran (180) and phenylpedluorobutylsulfonate (phenylnonaflate) (181) in the presence of (R)-BINAP (cf Chapter 7) Under normal pressure and at GO "C an enantiomeric excess of 47 % ee for 183 was achieved; when 1.0 GPa was applied, the enatioselectivity for 183 was improved to 89 % ee under otherwise unchanged conditions. It was assumed that under high pressure complexes of different stoichiometry may be formed which are more favorable towards a facial selective addition.…”

Section: High Pressure In Organic Synthesis: Influence On Selectivitymentioning

confidence: 74%