Improved Procedures for the Synthesis of 9,9-Disubstituted 9,10-Dihydroacridines.

We found that a previously reported synthesis of 9,9-disubstituted 9,10-dihydroacridines (DHAs) that relied on an acid-catalyzed cyclization was plagued by a competing elimination reaction, resulting in some elimination products being incorrectly identified as their structural isomer DHAs. In this report, we provide improved synthetic procedures for 9,9-disubstituted DHAs, demonstrated by the synthesis of two 9,9-diethyl DHAs.