Propargylic alcohols and azides are important classes of organic compounds that are accessible by straightforward methods. Their metal-free transformations in 1) direct nucleophilic substitution of propargylic alcohols 2) Meyer-Schuster rearrangement of propargylic alcohols and 3) thermolysis of triazolines to aziridines, have been developed. The direct substitution reactions of alcohols produce water as only by-product and have been identified by ACS Green Chemistry Institution Pharmaceutical Roundtable as a research priority area. We specifically focused on using commercially available phosphorus-based Brønsted acids in the direct amination of propargylic alcohols which is outlined in Chapter 1. Brønsted acids are particularly attractive catalysts compared to transition metals/Lewis acids due to their low cost, stability in air/moisture and easy separation from organic products. On the other hand, propargylamines are present in many pharmaceutical intermediates and natural products. A range of propargylamines were produced with our catalytic system, and a scope of the reaction was expanded to highly basic anilines and typical O-, C- and S- nucleophiles. Alternatively, this family of acids can mediate Meyer-Schuster rearrangements to access α,β-unsaturated carbonyl compounds as described in Chapter 2. The third topic is outlined in Chapter 3. Aziridines are useful organic synthons and their derivatives have shown important biological activity. Azide-alkene cycloaddition is valuable and atom economic methodology to access triazolines whose thermolysis might lead to aziridines upon heating through N2 extrusion. The reactions of azides and electron-deficient alkenes were investigated in toluene to selectively form aziridines over undesired imines. A broad scope of this thermolysis was explored and we found that selectivity of the reaction was strongly influenced by the substituents on the triazoline intermediate. Further reactivity of the obtained aziridines on nucleophilic ring-opening transformations is also detailed. In the end of each chapter, the corresponding Experimental Section, Additional Optimisation Studies and X-Ray Crystallographic Data are provided. General Conclusion and Future Work are included in the final section of this thesis.