λ-Orthogonal Pericyclic Macromolecular Photoligation

A photochemical strategy enabling -orthogonal reactions is introduced to construct macromolecular architectures and to encode variable functional groups with site-selective precision into a single molecule by the choice of wavelength. -Orthogonal pericyclic reactions proceed independently of one another by the selection of functional groups that absorb light of specific wavelengths. The power of the new concept is shown by a one-pot reaction of equimolar quantities of maleimide with two polymers carrying different maleimide-reactive endgroups, that is, a photoactive diene (photoenol) and a nitrile imine (tetrazole). Under selective irradiation at =310-350nm, any maleimide (or activated ene) end-capped compound reacts exclusively with the photoenol functional polymer. After complete conversion of the photoenol, subsequent irradiation at =270-310nm activates the reaction of the tetrazole group with functional enes. The versatility of the approach is shown by -orthogonal click reactions of complex maleimides, functional enes, and polymers to the central polymer scaffold.