As a sub-class of Nazarov reactions, the aza-Nazarov reactions, which have remarkable importance due to their use in the synthesis of five-ring nitrogen containing structures, are rarely studied. For the first time in the literature, the aza-Nazarov reaction was developed with 3,4-dihydroisoquinoline and α, β-unsaturated acyl chloride compounds operating under catalytic and moderate conditions with high efficiency, but the investigation and development studies of the proposed mechanism for this reaction were not conducted. The complete understanding of the mechanism has great importance for the development of advanced synthesis methods of this reaction and the diversification of its products. In the first part of this thesis, control experiments were conducted to examine the steps of this particular aza-Nazarov reaction mechanism; identification of the side-product, effectiveness of the achiral anion binding catalysts on this reaction, independent aza-Nazarov reactions of the minor and major isomers of the acyl chloride compounds, use of thiophene-based substrate and β-silicon stabilization effect on the mechanism with a different approach were investigated. In the second part of this thesis, a new photochemical [2 + 2] cycloaddition reaction was developed to achieve regio- and stereo-control by utilizing the 1,8-diolnaphthalene as a template molecule. With this method, unsymmetrical cyclobutane products were synthesized for the first time as well as symmetrical cyclobutane products using trans-cinnamic acid derivatives. The fact that this reaction is carried out in solid state without using solvent and no side-product formation is observed and the recovery of the template molecule accomplished at the end of this reaction greatly contributes to developments in green chemistry.