Silyl formates as hydrosilane surrogates for the transfer hydrosilylation of ketones

An energetically and atom economic transfer hydrosilylation of ketones employing silyl formates as hydrosilanes surrogates under mild conditions is presented. A total of 24 examples of ketones have been successfully converted to their corresponding silyl ethers with 61-99% yield in the presence of a PNHP-based ruthenium catalyst and silyl formate reagent. The crucial role of the ligand for the transformation is demonstrated.

Synthesis of deoxymannojirimycin using a Ruthenium-catalysed hydrogen borrowing reaction

<p>1-Deoxymannojirimycin (DMJ) has been investigated as a potential anti-cancer therapy due to its specific inhibition of class I α-mannosidase enzymes, which has been shown to trigger ER stress and the Unfolded Protein Response (UPR) pathway, leading to apoptosis in human hepatocarcinoma cells. Current methods for the synthesis of DMJ consist of multiple steps and often result in poor yields. The objectives of this research project were to develop a scale-up suitable synthesis of deoxymannojirimycin (DMJ), and to assess the feasibility of telescoping key-reactions to reduce the number of unit operations. Synthetic efforts focused on the key conversion of 1 to 2 have previously involved separate oxidation and reduction steps. In our laboratory; attempts to use hydrogen-borrowing chemistry had taken >48hr and not been achieved in high yield. The highlights of this work were that this conversion was ultimately realised in 95% yield in 24hr, and that the final deprotection of (2) could be telescoped into the process removing reaction-workup and chromatographic steps. The ruthenium catalyst used in the hydrogen borrowing reaction was found to be extremely air-sensitive, with reactions taking place in carefully prepared reaction vessels under an atmosphere of dry argon gas. The catalyst was also found to exhibit sensitivities to materials such as metal needles and polymer tubing, preventing sampling and monitoring of the reaction during synthesis. This study demonstrated that a one-pot synthesis is feasible,compressing the final steps in the synthesis of DMJ in excellent yield. The difficulty arises from the sensitive nature of the ruthenium catalyst, and the extreme care required in the preparation of the glassware and reagents used in synthesis. Many aspects of this development require further investigation, including the sampling, monitoring and quality control of each synthetic step.</p>

Synthesis of deoxymannojirimycin using a Ruthenium-catalysed hydrogen borrowing reaction

<p>1-Deoxymannojirimycin (DMJ) has been investigated as a potential anti-cancer therapy due to its specific inhibition of class I α-mannosidase enzymes, which has been shown to trigger ER stress and the Unfolded Protein Response (UPR) pathway, leading to apoptosis in human hepatocarcinoma cells. Current methods for the synthesis of DMJ consist of multiple steps and often result in poor yields. The objectives of this research project were to develop a scale-up suitable synthesis of deoxymannojirimycin (DMJ), and to assess the feasibility of telescoping key-reactions to reduce the number of unit operations. Synthetic efforts focused on the key conversion of 1 to 2 have previously involved separate oxidation and reduction steps. In our laboratory; attempts to use hydrogen-borrowing chemistry had taken >48hr and not been achieved in high yield. The highlights of this work were that this conversion was ultimately realised in 95% yield in 24hr, and that the final deprotection of (2) could be telescoped into the process removing reaction-workup and chromatographic steps. The ruthenium catalyst used in the hydrogen borrowing reaction was found to be extremely air-sensitive, with reactions taking place in carefully prepared reaction vessels under an atmosphere of dry argon gas. The catalyst was also found to exhibit sensitivities to materials such as metal needles and polymer tubing, preventing sampling and monitoring of the reaction during synthesis. This study demonstrated that a one-pot synthesis is feasible,compressing the final steps in the synthesis of DMJ in excellent yield. The difficulty arises from the sensitive nature of the ruthenium catalyst, and the extreme care required in the preparation of the glassware and reagents used in synthesis. Many aspects of this development require further investigation, including the sampling, monitoring and quality control of each synthetic step.</p>

Fractionation of Birch Wood by Integrating Alkaline-Acid Treatments and Hydrogenation in Ethanol over a Bifunctional Ruthenium Catalyst

For the first time, the fractionation of birch wood into microcrystalline cellulose, xylose and methoxyphenols is suggested based on the integration of alkali-acid pretreatments and hydrogenation in ethanol over a bifunctional Ru/C catalyst. It is established that removal of hemicelluloses during pretreatments of birch wood influences the yields of the liquid, gaseous and solid products of the non-catalytic and catalytic hydrogenation of pretreated samples in ethanol at 225 °C. The bifunctional Ru/carbon catalyst affects in different ways the conversion and yields of products of hydrogenation of the initial and acid- and alkali-pretreated birch wood. The most noticeable influence is characteristic of the hydrogenation of the acid-pretreated wood, where in contrast to the non-catalytic hydrogenation, the wood conversion and the yields of liquid products increase but the yields of the solid and gaseous products decrease. GC-MS, gel permeation chromatography and elemental analysis were used for characterization of the liquid product composition. The molecular mass distribution of the liquid products of hydrogenation of the initial and pretreated wood shifts towards the low-molecular range in the presence of the catalyst. From the GC-MS data, the contents of monomer compounds, predominantly 4-propylsyringol and 4-propanolsyringol, increase in the presence of the ruthenium catalyst. The solid products of catalytic hydrogenation of the pretreated wood contain up to 95 wt% of cellulose with the structure, similar to that of microcrystalline cellulose.