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.