Synthesis and Characterization of a Two Stage, Nonlinear Photobase Generator

Amine
photobase generators (PBGs) are uncommon yet useful compounds. Rarer
still are examples of PBGs that are active at visible wavelengths.
We report the synthesis and characterization of new photolabile amine
protecting groups that are active under visible light. The new chromophore,
benzothiophene imino-phenylacetonitrile (BTIPA), was synthesized in
four steps without use of chromatography and found to release any
one of several amines upon exposure to 405 nm light. The chromophore
was also demonstrated to be useful as a Merrifield synthesis protecting
group. Experimental evidence suggests a sequential, two stage photolysis
mechanism which leads to a nonlinear response to dose.