Temperature dependence of the distribution of trityl groups in the tritylation of 1,2-O-isopropylidene-α-D-glucofuranose

The tritylation reaction of 1,2-O-isopropylidene-alpha-D-glucofuranose with 2.4 molar amounts of trityl chloride in pyridine at 70 degrees C for 20 h gave the 5,6-di-O-trityl derivative in 50% yield as the major product, whereas the reaction at 115 degrees C mainly gave the 3,6-di-O-trityl derivative (26% yield) along with the CO-trityl derivative (48% yield). The fact that the yield of the 5,6-di-O-trityl derivative at 115 degrees C decreased after 1 h and was 12% at 20 h is due to the redistribution of trityl groups including detritylation assisted by pyridinium chloride. It was found that tritylation of the primary hydroxyl group at C-6 was almost completed within 10 min at 115 degrees C.