Theoretical Investigation of Methylpentynol-AzideIntermolecular Hbonding and Regiochemical Outcome of Its 1,3-DC Reactions

This study was focused on the theoretical and computational studies of the Hydrogen bondingeffect on the regioselectivity of the 1,3-dipolar cycloaddition (1,3-DC) reactions. 1,3-DC Reactionshave been applied in a number of diverse fields [1]. Stereochemistry in these reactionsis spotlight, recently [2]. The five-membered heteroaromatic rings that achieved by 1,3-DCwere widely used as an important role in various biochemical processes [3]. Here in,Methylpentynol (a) which is a treatment of insomnia was used as a dipolarophile. Cycloadditionof a to azide (b) can lead to regioselective 1,2,3-triazoles due to H-bonding between thehydrogen of azide (b) and the oxygen of hydroxy group in methylpentynol (a) as a hydrogenacceptor or H-bonding between the hetro atom of Azide (b) and the hydroxy group ofmethylpentynol (a) as a suitable hydrogen donor. In this study, the energy levels of the reactants(a,b), H-bonding arrays (c-e), transition state (TS), products (1,2), the free energies (inkcal mol-1) of reaction (ΔrG and ΔG#), rate constants by using Eyring s equation (k), structuraldata were calculated and obtained by DFT-B3LYP/6-31G* method.