Syntheses of Quaternary Carbon-Containing Oxazatricycle and Spiropyran Libraries via Multicomponent Reactions and Their Molecular Switching Properties

A practical protocol for the preparation of parallel solution-phase libraries of the quaternary carbon-containing oxazatricycles and spiropyrans is reported. Target compounds were obtained in moderate to excellent yields by an Et3N-mediated multicomponent reaction from various N-methylisoquinolium or flavylium salts and 4-hydroxycoumarins or dimedone in acetone. Purification of the final products by recrystallization in ethyl acetate/methylene chloride or by column chromatography allowed easy isolation of nine compounds of each array. Preliminary studies indicated that some of the prepared compounds exhibit redox switching, photochromic, and thermochromic properties.