In-plane aromaticity in 1,3-dipolar cycloadditions. solvent effects, selectivity, and nucleus-independent chemical shifts

The aromaticity and the regiochemistry of several 1,3-dipolar cycloaddition s have been studied computationally. It is found that all the transition st ructures associated with concerted supra-supra processes are in-plane aroma tic, and this aromaticity is compatible with a ring current circulating alo ng the molecular plane. Solvent effects enhance the activation barrier of t he reaction and diminish its synchronicity, with little impact on aromatici ty. According to our calculations,aromaticity is important but does not det ermine the regiochemistry of the reaction. Other phenomena such as electros tatic interactions and solvent effects can modify the regiochemical and the stereochemical outcome.