Synthesis of 1,8-dioxo-octahydroxanthene derivatives using NBS under mild conditions

An efficient one-pot synthesis of 1,8-dioxo-octahydroxanthene is achieved through a condensation of arylaldehydes and 5,5-dimethyl-1,3-cyclohexanedione in the presence of N-bromosuccinimid. This method enjoys several advantages such as low cost, simple work up procedure and safe reaction conditions. Graphical Abstract Table 1. Optimization of reaction condition. Entry Amount of NBS Condition Yield (%)a 1 0 mol % Reflux/ethanol/20 h 0 2 2 mol % 50°C/ethanol/12 h tr 3 2 mol % Reflux/ethanol/14 h 15 4 5 mol % Reflux/ethanol/14 h 30 5 10 mol % Reflux/ethanol/14 h 55 6 15 mol % Reflux/ethanol/14 h 80 7 20 mol % Reflux/ethanol/14 h 94 8 20 mol % MW/DMAC/5 min 90 a Isolated yield.