Ruthenium(II) complexes catalyze the insertion of sulfur dioxide into (het)aryl and alkenyl boronic acids. The transmetalation−sulfination process proceeds with DABSO in the presence of 5 mol % RuCl 2 (PPh 3 ) 3 in methanol at 100 °C. The intermediate sulfinate salt can be quenched with various electrophiles such as alkyl halides, epoxides, Michael acceptors, and λ 3 -iodanes in moderate to good yields. The reported sulfone synthesis can be performed either as a direct one-pot or one-pot twostep procedure depending on the reactivity of the electrophile.

Liquid SO2 is a polar solvent that dissolves both covalent and ionic compounds. Sulfur dioxide possesses also Lewis acid properties, including the ability to covalently bind Lewis basic fluoride ions in a relatively stable fluorosulfite anion (FSO2 −). Herein we report the application of liquid SO2 as a promoting solvent for glycosylation with glycosyl fluorides without any external additive. By using various temperature regimes, the method is applied for both armed and disarmed glucose and mannose-derived glycosyl fluorides in moderate to excellent yields. A series of pivaloyl-protected O- and S-mannosides, as well as one example of a C-mannoside, are synthesized to demonstrate the scope of the glycosyl acceptors. The formation of the fluorosulfite species during the glycosylation with glycosyl fluorides in liquid SO2 is proved by 19F NMR spectroscopy. A sulfur dioxide-assisted glycosylation mechanism that proceeds via solvent separated ion pairs is proposed, whereas the observed α,β-selectivity is substrate-controlled and depends on the thermodynamic equilibrium.

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The Doctoral Thesis has been prepared as a collection of thematically related scientific publications comprising five publications in the SCI journals, one patent of the Republic of Latvia, and one application for patent of the Republic of Latvia. We have carried out fundamental research on the applications of SO2 as a solvent and reagent in organic synthesis. We have developed several novel synthetic methods that represent the use of liquid SO2 as a solvent for chemical transformations that proceed via carbenium ion intermediates: a) hydration of aryl acetylenes; b) hydrohalogenation of aryl acetylenes; c) ring opening of methylenecyclopropanes with halides; d) glycosylation with glycosyl fluorides. By employing DABSO as an SO2 surrogate, we have also discovered the catalytic activity of Ru(II) complexes towards sulfonylative cross coupling reaction. This finding has been applied for the synthesis of sulfonyl derived compounds.