The azoxy(azo)-chromophore as π2-component in photo [2+2] cycloaddition reactions

Abstract Upon direct (sensitised) excitation selective metathesis is observed for the azoxy/ene 4 (with no intermediate being detectable at −50°C), quantitative [2+2] addition for the azo/ene 2. Thermally 4 undergoes uniform cycloaddition (t 1/2 (18°C) ca. 65 min) to the unusually stable 1,2,3-oxadiazolidine 3 (X-ray).