" A& ppm in CDC1,. Positive values represent upfield shifts. bAverage of upfield shifts for the atropisomers of 6b and Ib. with 7-bromo-l-tetraloneI0 which was converted (TsOH, PhCH,, Dean Stark, 92%) into its ethylene ketal 3 (Scheme I)." Metal-halogen exchange (2 equiv of t- BuLi, THF,-75" C) and subsequent addition to the lithium salt of 9-acridone (THF,-75 OC to room temperature) afforded acridinyl-substituted tetralone 4a in a 54% yield. I2 ...