V. Quasi-Anomeric Radical Stabilization
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- 23933
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Radicals centered at various carbon atoms in a pyranoid ring can be divided, on the basis of their stability, into two groups. The first group includes the pyranos-1-yl and pyranos-5-yl radicals, intermediates that are stable enough to be generated and observed in toluene or tetrahydrofuran. The second group, pyranosyl radicals centered at C-2, C-3, and C-4, cannot be observed in toluene or tetrahydrofuran because they abstract hydrogen atoms from these solvents too rapidly.15 Since only the pyranos-1-yl and pyranos-5-yl radicals are capable of experiencing stabilization from the quasi-anomeric effect (Figure 8), the special stability of these radicals provides further support for the existence of quasi-anomeric stabilization.
