Deoxy‐nitrosugars. 11th Communication. Reactions of 1‐C‐nitroglycosyl halides and 1‐C‐nitroglycosyl sulfones with dialkyl‐phosphite anions: Nucleophilic attack vs. single‐electron transfer

Treatment of the chloro‐nitro‐ribofuranose 7 with KPO(OMe)2 gave the O‐amino phosphate 8 (5 %) and the nitrile 9 (62 %). Compound 9 was also obtained by the reaction of 8 with KPO(OMe)2, and its structure was established by X‐ray analysis. Treatment of the chloro‐nitro‐mannofuranose 10, the bromo‐nitro‐ribofuranose 14, or the bromo‐nitro‐mannofuranose 16, respectively, with the K or Na salt of HPO(OMe)2 lead also to O‐amino phosphates and nitriles. The (1‐C‐nitroglycosyl)phosphonate 22 was obtained (21 %) together with the nitrile 21 (51 %) from the chloro‐nitro‐mannofuranose 10 and KPO(OEt)2. The reaction of the 1‐C‐nitroglycosyl sulfone 25 (NO2‐group endo) with KPO(OEt)2 gave the (1‐C‐nitroglycosyl)phosphonate 22 (61%) and the nitrile 21 (11 %), whilst the anomeric sulfone 26 (NO2‐group exo) gave 22 (15 %) and 21 (58 %). In the presence of [18] crown‐6, a mixture of the anomers 25 and 26 gave the (1‐C‐nitroglycosyl)phosphonate 22 in 67 % yield together with 21 (13 %). These findings are rationalized as the result of a competition between a nucleophilic attack of the dialkyl‐phosphite anions on the NO2‐group leading ultimately to the nitrile 21 and a single‐electron transfer reaction leading to the (1‐C‐nitroglycosyl)phosphonate 22.