Two-Photon Sensitive Coumarinyl Photoremovable Protecting Groups With Rigid Electron-Rich Cycles Obtained By Domino Reactions Initiated By A 5-Exo-Dig Cyclocarbopalladation

We herein report the design, synthesis, and photophysical characterization of extended and rigid coumarinyl derivatives showing large two-photon sensitivities (delta(a)Phi(u) <= 125 GM) at 740 and 800 nm. To efficiently synthesize these complex photoremovable protecting groups (PPGs), we used step-economic domino reactions. Moreover, those new coumarinyl PPGs display unique bathochromic shifts (<= 100 nm) of the uncaging sub-products as a result of the formation of a more conjugated fulvene moiety.