Citrus Peel Additives for One-Pot Triazole Formation by Decarboxylation, Nucleophilic Substitution, and Azide–Alkyne Cycloaddition Reactions

This undergraduate organic laboratory experiment consists of three different reactions occurring in the same flask: a cycloaddition reaction, preceded by decarboxylation and nucleophilic substitution reactions. The decarboxylation and cycloaddition reactions occur using identical Cu(I) catalyst and conditions. Orange, lemon, and other citrus fruit peels and juices in the presence of CuSO 4 lead to the Cu(I)-catalyzed decarboxylation of 3-phenyl-2-propynoic acid to give ethynylbenzene. These click chemistry conditions give Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) of 2-azido-1-phenylethanone with ethynylbenzene to afford 1-phenyl-2-(4-phenyl-1 H -1,2-3-triazol-1-yl)ethanone regioselectively.