Synthesis of a crystallochromic indolizine dye by a base- and catalyst-free photochemical route

Abstract

Indolizine derivatives are obtained by irradiation of 2-benzoyl-N-benzylpyridinium derivatives and dimethyl acetylene dicarboxylate, thus providing a competitive and complementary base- and catalyst-free synthesis. With this method, the first example of a crystallochromic indolizine is presented, whose color in the solid state depends on the out-of-plane torsion of the benzoyl substituent.