Anders Dahlen

Instantaneous SmI2–H2O-mediated reduction of dialkyl ketones induced by amines in THF

Abstract Reduction of various ketones to their corresponding alcohols is shown to be instantaneous, i.e. completed in less than 10 s, by samarium diiodide (2.5 equiv.) in the presence of water (6.25 equiv.) and an amine (5 equiv.) in THF. The rates of reduction of ketones in this mixture exceed by far the rates determined by an amine or water alone. Rate enhancement is at least 100 000 compared to the reduction without a proton source, or at least 100 times faster than the rate of the widely used HMPA/alcohol accelerated reductions. This new method is therefore suggested to be an excellent replacement of the toxic HMPA/alcohol method.

Selective reduction of carboncarbon double and triple bonds in conjugated olefins mediated by SmI2/H2O/amine in THF

Conjugated double and triple bonds are reduced into alkenes using non-hazardous SmI2/H2O/amine mixtures as reducing agents in THF. Isolated alkenes are not reduced during these reductions. All the reactions studied are quantitative and are completed in less than five minutes.

Chelating alcohols accelerate the samarium diiodide mediated reduction of 3-heptanone

Abstract Initial rate studies of samarium diiodide mediated reduction of 3-heptanone to 3-heptanol are reported. The reduction of 3-heptanone with the polydentate tri(ethylene glycol) methyl ether is 16 times faster than without a proton donor, and 4.3 times faster than methanol. The primary kinetic isotope effect (KIE) was measured as k H / k D ≈2, indicating a rate-determining proton transfer. Diols are superior to mono-alcohols as proton donors, the reduction of 3-heptanone is 255 times as fast with di(ethylene glycol) than in the absence of a proton donor. A mechanism of glycol accelerated samarium diiodide reduction is discussed.

Synthesis of Diverse α-Fluoroalkoxyaryl Derivatives and their Use for the Generation of Fluorinated Macrocycles

Introduction of difluorinated functionality has emerged as a powerful means for conformational design with minimal steric footprint. Synthetic approaches for the preparation of aryl difluoromethylene ether containing novel building blocks were established, enabling the inclusion of the aryl difluoromethylene ether system into macrocyclic scaffolds for the first time.