Mechanisms and Transition States of 1,3-Dipolar Cycloadditions of Phenyl Azide with Enamines: A Computational Analysis

The transition structures for the 1,3-dipolar cycloadditions of phenyl azide to enamines derived from acetophenone or phenylacetaldehyde and piperidine, morpholine, or pyrrolidine were located using quantum mechanical methods. These cycloadditions were studied experimentally in 1975 by Meilahn, Cox, and Munk (J. Org. Chem. 1975, 40, 819-823). Calculations were carried out with M06-2X/6-311+G(d,p), SCS-MP2/6-311+G(d,p)//M06-2X/6-311+G(d,p), and B97D/6-311+G(d,p) methods with the IEF-PCM solvation model for chloroform and ethanol. The distortion/interaction model was utilized to understand mechanisms, reactivities, and selectivities.