DFT based study on the mechanism of an unexpected reaction of aldehydes with 1,3-dicarbonyl compounds

The mechanism of an unexpected reaction between two molecules of 1,3-dicarbonyl compound and one molecule of the aldehyde to selectively provide spiro dihyrofuran and cyclopropane derivatives promoted by molecular iodine and dimethylaminopyridlne has been Investigated by density functional theory based approach. The geometries and the frequencies of reactants, intermediates and transition states are calculated using Becke three parameter exchange and Lee-Yang-Parr correlation functional. The vibrational analysis, Intrinsic reaction coordinate (IRC) calculation and ESP analysis verify the authenticity of the transition states. Depending on substitution pattern of 1,3-dicarbonyl compound, there may be two pathways, one leads to furan derivative and the other to cyclopropane derivative. The nucleus independent chemical shift (NICS) values have been calculated for the intermediates, products and the corresponding transition states to ensure the aromaticity contribution to the reaction pathway. The results are In good agreement with the experimental findings.