Norrish-Yang Cyclization of Imidazolidinone Derivatives in the Presence and Absence of Tetraalkylammonium Salts.

Norrish-Yang cyclization reactions have attracted much attention in synthetic organic chemistry due to their ability to activate and functionalize inactive CH positions. In this study, we report that the diastereoselective course of the Norrish-Yang reaction of imidazolidinone derivatives is reversed by the addition of tetrabutylammonium salts (TBAX). 1H NMR experiments suggested that cation-π interactions between TBA+ and the substrate control the reactive conformation of this latter species. In the course of this study, we found that unexpected compounds with 6/7/5- and 6/6/5-fused tricyclic systems containing an aromatic ring were also formed in the presence and absence of TBAX, respectively. Furthermore, we report the formation of an unexpected fused tetracyclic compound, the framework structure of which resembles that of a tetraquinane, when a substrate with 2-benzoylethyl side chains on both nitrogen atoms of the imidazolidinones is used.