Computation has guided the design of conformationally-strained dioxolane-fused trans-cyclooctene (d-TCO) derivatives that display excellent reactivity in the tetrazine ligation. A water soluble derivative of 3,6-dipyridyl-s-tetrazine reacts with d-TCO with a second order rate k2 366,000 (+/− 15,000) M−1s−1 at 25 °C in pure water. Furthermore, d-TCO derivatives can be prepared easily, are accessed through diastereoselective synthesis, and are typically crystalline bench-stable solids that are stable in aqueous solution, blood serum, or in the presence of thiols in buffered solution. GFP with a genetically encoded tetrazine-containing amino acid was site-specifically labelled in vivo by a d-TCO derivative. The fastest bioorthogonal reaction reported to date [k2 3,300,000 (+/− 40,000) M−1s−1 in H2O at 25 °C] is described herein with a cyclopropane-fused trans-cyclooctene. d-TCO derivatives display rates within an order of magnitude of these fastest trans-cyclooctene reagents, and also display enhanced stability and aqueous solubility.

The synthesis of ureas from amines has traditionally been accomplished with stoichiometric reactions of phosgene or its derivatives, which are associated with environmental and waste disposal issues. Because of the prevalence of urea moieties in molecules of interest for several applications, alternative catalytic routes for the oxidative conversion of amines to ureas using CO as the carbonyl source have been developed. This microreview discusses recent developments in transition metal‐catalyzed oxidative carbonylation of amines to ureas as an alternative to phosgene and its derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Novel mixed-ligand rhodium(II) paddlewheel complexes incorporating tethered axial thioether ligands have been synthesized and characterized. The thioether moiety is essential for high yields and the suppression of byproducts in cyclopropanation reactions using an electron-deficient diazoacetate. Crystal structures, UV−vis analysis, and cyclic voltammetry experiments shed light on the catalytic performance of the complexes.

The effect of tethering a thioether to a rhodium(II) paddlewheel complex are evaluated in Si–H insertion reactions. This study provides further evidence for the benefits of incorporating thioethers into the rhodium paddlewheel motif. When using a tethered complex, the in situ carbenoid formation and subsequent Si–H insertion are not impeded, yields are improved by up to 12 % at elevated temperatures, and selectivity for diazo compounds is greater when compared to non‐tethered catalysts. Computational modelling of the complexes is also presented in order to rationalize the results.

Dirhodium(II) paddlewheel complexes have high utility in diazo-mediated cyclopropanation reactions and ethyl diazoacetate is one of the most commonly used diazo compounds in this reaction. In this study, we report...