Assessment of mechanistic hypotheses of 1,3-dipolar cycloaddition of (arylsulfonyl)allene to nitrilimines by DFT reactivity indices

The mechanism of 1,3-dipolar cycloaddition between 1-[2-(acetylamino)phenylsulfonyl]-1,2-propadiene 1 and a series of N-(4-substituted)phenyl-C-methoxycarbonylnitrilimines 2 has been reinvestigated on the basis of DFT calculations and a quantitative formulation of the HSAB principle. Comparison of the new computational results with experimental findings led to the formulation of a mechanistic scheme involving both 1,3-prototropic and 1,3-arylsulfonyl shifts. The role of silver cation is also pointed out. (C) 2003 Elsevier Science Ltd. All rights reserved.