Protecting-Group-Free Site-Selective Reactions in a Metal–Organic Framework Reaction Vessel

Site-selective organic transformations are commonly required in the synthesis of complex molecules. By employing a bespoke metal–organic framework (MOF, 1·[Mn(CO)3N3]), in which coordinated azide anions are precisely positioned within 1D channels, we present a strategy for the site-selective transformation of dialkynes into alkyne-functionalized triazoles. As an illustration of this approach, 1,7-octadiyne-3,6-dione stoichiometrically furnishes the mono-“click” product N-methyl-4-hex-5′-ynl-1′,4′-dione-1,2,3-triazole with only trace bis-triazole side-product. Stepwise insights into conversions of the MOF reaction vessel were obtained by X-ray crystallography, demonstrating that the reactive sites are “isolated” from one another. Single-crystal to single-crystal transformations of the Mn(I)-metalated material 1·[Mn(CO)3(H2O)]Br to the corresponding azide species 1·[Mn(CO)3N3] with sodium azide, followed by a series of [3+2] azide–alkyne cycloaddition reactions, are reported. The final liberation of the “cl...