2-Propanol, trityl ether

The simple alcohols whose trityl ethers have been prepared by treatment with trityl chloride and pyridine include, in addition to primary alcohols, 2-propanol, cyclohexanol, Z-menthol, d-borneol, and cholesterol. Trityl ethers involving the secondary hydroxyl group in glycerol are also known. - There can be no doubt, therefore, that secondary as well as primary hydroxyl groups react with trityl chloride in pyridine. 

The relative ease of acid-catalysed hydrolysis (0.53 M sulfuric acid in 2 1 aqueous 2-propanol at room temperature) follows the order cyclopentylidene > isopropylidene > cyclohexylidene. For example, the half life for the hydrolysis of 1,2-0-alkylidene-cx-D-glucopyranoses followed the order cyclopentylidene (8h), isopropylidene (20 h), cyclohexylidene (124 h).57 The higher acid lability of cyclopentylidene acetals has been frequently exploited in synthesis. Thus, aqueous or ethanolic acetic acid at room temperature is able to liberate a 1,2-diol in the presence of an isopropylidene group [Scheme 3.37],5R an 0-trityl group [Scheme 3.38]59 and a p-methoxybenzyl ether but not a tetrahydropyra-nyl group [Scheme 3.39],60... 

The tritylation of 5 was performed in pyridine using standard procedures. Reaction mixtures were worked-up by water quenching followed by filtration and recrystallization of the crude product. Recrystallization of the crude product was done from 2-propanol containing small amounts of triethylamine. The addition of triethylamine was necessary to avoid the formation of trityl isopropyl ether by solvolysis of the product when heated in 2-propanol. The yield of the product in this step was 75-80%. Impurities such as ethyl glyoxylate diethyl acetal carried over from previous steps were removed during the isolation of 6. 

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