Sulfoxides and sulfones create a set of chemical compounds, that show biological activity. That is why we can find a lot of different pharmaceutical compounds that include either sulfoxide or sulfone group. As variety of different sulfur compounds grows everyday, there is also a growth in synthesis of such chemicals. We can find more and more different so called green routes of synthesis, which include reactants that present minimum burden to our living environment. In this undergraduate degree I studied selectivity of aerobic oxidation of aromatic sulfides with usage of nitric(V) acid and iron ions as catalysts in fluorinated alcohols. I varied solvents and their amounts, temperature and catalysts and its quantity. I succeded to obtain the wanted sulfoxide of dibenzotiophene, dibenzo[b,d]tiophene 5-oxide with a yield of 72%. Same oxidation method was also applied on thianthren which sulfoxides were isolated. Thianthren 5-oxide with a 41% yield and two thianthren dioxides cis-thianthren 5,10-dioxide with a 5,5% yield and trans-thianthren 5,10-dioxide with a 30% yield.