An Easily Accessible Isospiropyran Switch

In the presence of SiCl4, three molecules of 5′−bromo−2′−hydroxyacetophenone 2 underwent tandem aldol condensation to give isospiropyran 1 in 69% yield. Acid (CH3SO3H), silica and elevated temperature prompted a scission of the Cspiro−O chromene bond in 1 turning it into its conjugated and colored form. A facile access to chromic 1, reported herein, opens a way for rapid diversification of these structurally unique switches and optimization of their action for incorporation into dynamic materials.