Recently Tanner1 andOno2 have observed that secondary and tertiary nitro compounds can be reductively denitrated by tri-butyltin hydride. They suggested that this chain reaction may involve a one-electron transfer from the tin radical to the nitro compound as a key step in the reaction, thereby resembling the denitration with (a) the sodium salt of methanthiol, 3 (b) KOH in ethylene glycol, 4 and (c) N-benzyl-1, 4-dihydronicotinamide. 5 Vasella6 has appliedthis tin hydride reduction to nitro sugars 1, and 6 which gave C-glucosidesin good yields. We have now proved that in this tin hydride reaction a nitro radical anion with a tributyltin cation as counterion is involved and that nitro com-pounds can be used as precursors for radical CC bond-forming reactions.

By following the reaction of 1 with Bu3SnH by ESR spec-troscopy under photolytic7 or AIBN-initiated8 conditions a 1: 1: 1 triplet is observed with a coupling constant of 25.75±0.05 G and a g value of 2.005 43 (Figure 1). These data are typical for nitro group radical anions. 9 Eachhyperfine line of the triplet is surrounded by a doublet with an intensity of ca. 12% which arises from the nearly equivalent couplings of 3.0-3.4 G (depending on the solvent) of the tin isotopes 119Sn and 117Sn. 10 11Analogous results were obtained by irradiating a THF solution of hexamethylditin in presence of 1.