Chemical studies of carbohydrates. Part I. Conversion of derivatives of glucose and allose into pyrazoles and pyridazines

On reaction of 1,2:5,6‐di‐ O ‐isopropylidenc‐3‐ O ‐( p ‐tolylsulfonyl)‐α‐D‐glueofuranose ( 1 ) with hydrazine hydrate at 140° besides formation of 3‐deoxy‐3‐hydrazino‐1,2:5,6‐di‐ O ‐isopropylidene‐α‐D‐allofuranose ( 2 ) and 3‐dcoxy‐1,2:5,6‐di‐ O ‐isopropylidene‐α‐D‐ erythro ‐hex‐3‐enofuranose ( 3 ), ring transformation into 3‐[4′‐(2′,2′‐dimethyl‐1′,3′‐dioxolanyl)]pyridazine ( 4 ) takes place. At 170°, however, only 2 and 4 are formed, indicating that 3 is the precursor of 4. Treatment of 3 with hydrazine hydrate at 170° indeed gives a nearly quantitative ring expansion into 4. Treatment of 3‐dcoxy‐3‐hydrazino‐1,2:5,6‐di‐ O ‐isopropylidenc‐α‐D‐glucofuranose ( 8 ) as well as the stereoisomeric allofuranose 2 with concentrated hydrochloric acid gives a nearly quantitative ring interconversion into 3‐(D‐ erythro ‐trihydroxypropyl)pyrazole ( 9 ).