Herein a new ¹¹C radiolabelling strategy for the fast and efficient synthesis of thioureas and related derivatives using the novel synthon, ¹¹CS₂, is reported. This approach has enabled the facile labelling of a potent progesterone receptor (PR) agonist, [¹¹C]Tanaproget, by the intramolecular reaction of the acyclic aminohydroxyl precursor with ¹¹CS₂, which has potential applications as a positron emission tomography radioligand for cancer imaging.

A glass-fabricated microfluidic device was used to screen a series of homogeneous alkene hydrogenation reactions by using Wilkinson’s catalyst. Good to excellent conversions were achieved for a range of alkene substrates within short reaction times (<2 min) and low hydrogen pressures (<0.2 MPa). During the course of the screening procedure, a metallic Rh layer was found to build up on the channels of the microfluidic device. Further investigation of this layer revealed that it was a highly active catalyst for the hydrogenation of alkenes, enones, and alkynes. Furthermore, this Rh layer catalyzed the hydrogenation of toluene to methylcyclohexane.

[¹¹C]Carbon monoxide is undoubtedly a highly versatile radiolabelling synthon with many potential applications for the synthesis of positron emission tomography (PET) tracer molecules and functional groups, but why has it not found more applications in the PET radiolabelling arena? Today, ¹¹CO radiolabelling is still primarily viewed as a niche area; however, there are signs that this is beginning to change as some of the technical and chemistry challenges of producing, handling and reacting ¹¹CO are overcome. This mini review covers the more recent developments of ¹¹CO-labelling chemistry and is focused on palladium and rhodium-mediated carbonylation reactions that are growing in importance and finding wider application for carbon-11 PET radiotracer development. Copyright © 2014 John Wiley & Sons, Ltd.

The evaluation and selection of the most appropriate catalyst for a chemical transformation is an important process in many areas of synthetic chemistry. Conventional catalyst screening involving batch reactor systems can be both time-consuming and expensive, resulting in a large number of individual chemical reactions. Continuous flow microfluidic reactors are increasingly viewed as a powerful alternative format for reacting and processing larger numbers of small-scale reactions in a rapid, more controlled and safer fashion. In this study we demonstrate the use of a planar glass microfluidic reactor for performing the three-component palladium-catalysed aminocarbonylation reaction of iodobenzene, benzylamine and carbon monoxide to form N-benzylbenzamide, and screen a series of palladium catalysts over a range of temperatures. N-Benzylbenzamide product yields for this reaction were found to be highly dependent on the nature of the catalyst and reaction temperature. The majority of catalysts gave good to high yields under typical flow conditions at high temperatures (150 °C), however the palladium(II) chloride-Xantphos complex [PdCl₂(Xantphos)] proved to be far superior as a catalyst at lower temperatures (75–120 °C). The utilised method was found to be an efficent and reliable way for screening a large number of palladium-catalysed carbonylation reactions and may prove useful in screening other gas/liquid phase reactions.

This mini-review covers the issues concerning the application of microfluidics towards radiolabelling with short-lived isotopes used for PET (positron emission tomography), and surveys the literature in this area. The application of microfluidic reactors to radiolabelling reactions is currently receiving a great deal of interest because of the potential advantages they have over conventional labelling systems. The volume and variety of radiolabelling reactions for PET is expected to grow markedly over the coming years due to increased demands for PET scanning. High demands and expectations for radiolabelled compounds will have to be met by exploiting new types of chemistry and technologies, such as microfluidics, to improve the production and development of PET tracers. Copyright © 2008 Society of Chemical Industry

Die Positronenemissionstomographie (PET) ist eine leistungsfähige Bildgebungsmethode, die zur Untersuchung und Visualisierung der menschlichen Physiologie eingesetzt wird. Das Funktionsprinzip der PET beruht auf der Detektion positronenemittierender Radiopharmazeutika. Aus PET-Experimenten können direkte Informationen über Stoffwechselvorgänge, Rezeptor-Enzym-Funktionen und biochemische Mechanismen im lebenden Gewebe erhalten werden. Anders als die Magnetresonanztomographie (MRT) und die Computertomographie (CT), die in erster Linie anatomische Bilder liefern, kann die PET chemische Veränderungen messen, die bereits vor dem Auftreten anatomischer Krankheitszeichen auftreten. Die PET ist dabei, sich als eine revolutionäre Methode für die Diagnostik von Körperfunktionen zu etablieren, die die Anwendung individueller, auf den Patienten zugeschnittener Behandlungsmethoden ermöglicht. Allerdings ist die Entwicklung von Synthesestrategien für neuartige positronenemittierende Moleküle nicht trivial. In diesem Aufsatz diskutieren wir die entscheidenden Aspekte bei der Synthese von PET-Radiotracern mit den kurzlebigen Positronenemittern ¹¹C, ¹⁸F, ¹⁵O und ¹³N. Der Schwerpunkt liegt auf den jüngsten Fortschritten bei der Entwicklung von Radiomarkierungsstrategien. Wir hoffen, dass dieser Aufsatz das Interesse von Synthesechemikern auch außerhalb der Radiochemie finden wird und die Bedeutung der PET in der molekularen Bildgebung sowie den Bedarf an neuen, innovativen chemischen Strategien für verbesserte Radiomarkierungstechniken aufzeigt.

Positron emission tomography (PET) is a powerful and rapidly developing area of molecular imaging that is used to study and visualize human physiology by the detection of positron-emitting radiopharmaceuticals. Information about metabolism, receptor/enzyme function, and biochemical mechanisms in living tissue can be obtained directly from PET experiments. Unlike magnetic resonance imaging (MRI) or computerized tomography (CT), which mainly provide detailed anatomical images, PET can measure chemical changes that occur before macroscopic anatomical signs of a disease are observed. PET is emerging as a revolutionary method for measuring body function and tailoring disease treatment in living subjects. The development of synthetic strategies for the synthesis of new positron-emitting molecules is, however, not trivial. This Review highlights key aspects of the synthesis of PET radiotracers with the short-lived positron-emitting radionuclides ¹¹C, ¹⁸F, ¹⁵O, and ¹³N, with emphasis on the most recent strategies.