A Typical NEDDA Cycloaddition Strategy between C-3-and N-Substituted Indoles and Butadienes Using Silica-supported Copper Triflate as an Efficient Catalytic System: A Correlative Experimental and Theoretical Study

The present paper elicits a [4+2] Diels-Alder cycloaddition strategy between C-3- and N-substituted indoles I-1 to 1-6 with two dienes of different nucleophilicity using silica-supported Cu(OTf)(2). Theoretical studies computed at the B3LYP/6-311G(d) level of theory reveal that all the indoles undertaken behave as electron-poor dienophiles and, therefore, prefer to participate through a normal electron demand Diels Alder (NEDDA) pathway. The analysis of the local reactivity descriptors further ascertained the completely regioselective outcome of the reaction profile.