Neal, Taylor A. Eippert, Allyson B. Chivington, Austin Jamison, Andrew Chukwuma, P. Chukwunalu Moore, Curtis E. Neal, Jennifer F. Allen, Heather C. Wysocki, Laura M. Paul, Noel M. Badjić, Jovica D. One-Pot Aldol Cascade for the Preparation of Isospiropyrans, Flavylium Salts, and bis-Spiropyrans We probed tandem aldol condensations of sixteen <i>o</i>-hydroxyacetophenones, carrying electron-withdrawing and -donating groups at positions 4 and 5, using five molar equivalents of SiCl<sub>4</sub> in anhydrous ethanol. Substrates carrying electron-withdrawing groups (EWGs) (0 < ∑σ > 0.63) populated the equilibria with isospiropyrans (12–74% yield), while those carrying electron-donating groups (EDGs) (∑σ < −0.31) gave flavylium salts (50–80%) or thermochromic bis-spiropyrans (73%). The results are of interest for developing novel organic materials possessing switchable photochromic and thermochromic characteristics. electron-withdrawing groups;SiCl 4;switchable photochromic;electron-donating groups;positions 4;Flavylium Salts;thermochromic characteristics;EWG;tandem aldol condensations;EDG;One-Pot Aldol Cascade;molar equivalents 2020-06-11
    https://acs.figshare.com/articles/journal_contribution/One-Pot_Aldol_Cascade_for_the_Preparation_of_Isospiropyrans_Flavylium_Salts_and_bis-Spiropyrans/12465143
10.1021/acs.joc.0c00825.s001