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1,8-Dioxo-octahydroxanthenes have efficiently been synthesized from 5,5-dimethyl-1,3-cyclohexanedione and aromatic aldehydes using silica supported sodium hydrogen sulfate (NaHSO 4 ·SiO 2 ) or silica chloride as a heterogeneous catalyst. The experimental procedure is very simple and the products are formed in high yields.
Silica chloride has been found to be an efficient catalyst for facile tosylation of alcohols directly with p-toluenesulfonic acid in methylene chloride under reflux. The process is associated with selective tosylation of secondary alcohols over primary alcohols.
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