New class of Reagents for Alkynylation and Cyanation
Scientists from the University of Göttingen developed novel reagents to attach terminal C-C or C-N triple bonds to organic molecules. These novel, sulfur based reagents have two striking advantages over the widely used EBX based reagents: They do not suffer from being potentially explosive but still show high alkynylation rates with yields up to 90% and the reduced reactivity allows for selection of alkynylation sites in one molecule.
The chemical versatility of the carbon-carbon triple bond is of high importance for the synthesis of fine chemicals. Therefore, reagents to facilitate alkynylation (the introduction of a carbon-carbon triple bond) are highly desirable, not only for industrial chemistry but also for biological and medical applications.
The inventors used transition-metal catalysis to perform electrophilic alkynylations, using the backbone of the Umemoto reagent (a dibenzothiophene). They developed a new class of alkynylation reagents, the 5-(alkynyl)dibenzothiophenium triflates, which can be synthesized with high efficiency (Figure1).
Figure 1) Synthesis of 5-(Akynyl)benzolthiophenium triflates:
In contrast to EBX-based reagents, they do not have the inherent tendency to explode, show an improved chemoselectivity for thiols and they can transfer alkyne groups to Amides.
These properties of 5-(Akynyl)benzolthiophenium triflates makes them a n in many cases superior alternative to the currently preferred EBX-alkynylation reagents.
Terminal alkynes, are valuable in the synthesis of of fine chemicals in industry as well as for scientific and medical applications. As a result of not beeing explosive, the synthesis of these alkynylation reagents can be upscaled. Reagents to attach alkyne-groups to chemicals are needed as basis for complex synthesis and could be used universally. The increased selectivity allows for selective transfer of alkyne-groups, even in makromolecules.
The superior properties of lead compounds from this class of Reagents are proven experimentally in laboratory scale.
We have filed a PCT patent application, which puts us in a position to offer worldwide licensing rights.(Applicant: Georg-August-Universität Göttingen public law foundation).
Publication Waldecker et al. (https://doi.org/10.1002/anie.201807418)
Dr. Martin Andresen