A DFT study of the polar Diels–Alder reaction between 4-aza-6-nitrobenzofuroxan and cyclopentadiene

The polar Diels–Alder reaction between 4-aza-6-nitrobenzofuroxan (ANBF) and cyclopentadiene has been studied using DFT procedures at the B3LYP/6-31G* level. Only one highly asynchronous transition state structure associated to the formation of the [4+2] adduct is found. A further [3,3] sigmatropic shift on the [4+2] cycloadduct allows its conversion into the thermodynamically more stable [2+4] cycloadduct . The analysis of the global and local electrophilicities of the reagents correctly explain the behaviour of ANBF as a strong electrophile in polar cycloadditions.