Sequential SNAr and Diels-Alder reactivity of superelectrophilic 10π heteroaromatic substrates

Using the DFT concept of global electrophilicity (omega), it is shown that 4,6-dinitro-7-chloro-benzo-furoxan and -benzofurazan are two 10 pi-heteroaromatics that rank to the top of the omega scale, comparing well with the related 4,6-dinitrobenzofuroxan reference. This superelectrophilic behaviour is demonstrated by the high propensity of these chloro-substituted superelectrophiles to undergo SNAr substitutions with an extremely weak carbon nucleophile such as 1,3,5-trimethoxybenzenze (pK(a)(H2O)=-5.72). The resulting TMB-substituted products are still ranking in the superelectrophilic region, making it possible to engage these compounds in Normal and Inverse electron demand [4+2] cycloadditions and [3+2] cycloaddition, which proceed with high regioselectivity and high stereoselectivity. (C) 2016 Elsevier Ltd. All rights reserved.