In many significant natural products, furans are a key motif. These oxygen-containing five-membered heterocycles are also versatile building blocks in the construction of highly complex target structures. As such, they are important scaffolds in organic and pharmaceutical chemistry.
As reported in the European Journal of Organic Chemistry, A. Stephen K. Hashmi and a team at Universität Heidelberg (Germany) have now introduced a general protocol for the preparation of highly substituted furans through a gold-catalyzed cyclization reaction.
The efficiency of reactions is often thought of in terms of atom economy, and the search for more efficient alternatives to classical chemical reactions is now an area of intense research. In this context, transition-metal catalysts are becoming a popular choice amongst chemists, because they are often used in only very small amounts, which conforms to the atom-economy rule and minimizes waste. Notably, in contrast to the often harsh conditions required to perform classical chemical transformations, most transition-metal catalyzed reactions can be performed under mild reaction conditions and within a short timeframe.
Because gold catalysts are robust, their popularity has increased significantly in the last few years. Gold catalysts can easily be handled in air, and they are also tolerant to water. Moreover, gold catalysts often show higher activity and higher selectivity than their more popular palladium counterparts. Gold is particularly well suited for substrates that bear a triple carbon–carbon bond (i.e., an alkyne), as it coordinates preferentially to this bond, resulting in a highly reactive complex that is prone to attack. As such, the gold-catalyzed cyclization of an alkyne tethered to an alcohol can provide easy access to highly substituted furans.
The German research team found that the gold(I)-catalyzed cyclization of various 2-alkynylallyl alcohols proceeded well and afforded the desired furan products with the use of low catalyst loadings under very mild reaction conditions. Importantly, both di- and trisubstituted furans could be obtained, which allows structural variety in the building blocks. Bifunctional substrates could also be cyclized to provide chemically interesting bisfurans. This synthetically simple route provides quick and easy access to highly substituted furan building blocks, which may help to facilitate the study of this important class of compounds.
Author: A. Stephen K. Hashmi, Universität Heidelberg (Germany),
Title: Cyclization of 2-Alkynylallyl Alcohols to Highly Substituted Furans by Gold(I)–Carbene Complexes
European Journal of Organic Chemistry, Permalink to the article: http://dx.doi.org/10.1002/ejoc.201001479
A. Stephen K. Hashmi | Wiley-VCH
Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute
Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy