π-Stacked dimers in 6-methoxy-3,3-dimethyl-3H-benzo[f]chromene, and centrosymmetric dimers containing C—H...π(arene) hydrogen bonds in racemic 3-bromo-2,2,6,6-tetramethyl-3,4-dihydro-2H,6H-1,5-dioxatriphenylene

Abstract

The title compounds, namely 6-methoxy-3,3-dimethyl-3H-benzo[f]chromene, C(16)H(16)O(2), (III), and racemic 3-bromo-2,2,6,6-tetramethyl-3,4-dihydro-2H,6H-1,5-dioxatriphenylene, C(20)H(21)BrO(2), (IV), were both synthesized in one-step regioselective Wittig reactions from substituted 1,2-naphthoquinones. The new ring in both compounds adopts a screw-boat conformation. A single pi-pi stacking interaction links the molecules of (III) into centrosymmetric dimeric aggregates, and a single C-H...pi(arene) hydrogen bond links the molecules of (IV) into centrosymmetric dimers.