THE MECHANISM OF SOLVOLYSIS OF 2-ADAMANTYL AZOXYTOSYLATE - ISOTOPIC LABELING, MEDIUM EFFECT, AND ATTEMPTED DEOXYGENATION STUDIES

Rates of solvolysis of 2-adamantyl azoxytosylate (1) have been measure d over a range of temperatures in ethanoic acid, methanoic acid, 50:50 (v/v) trifluoroethanol:water, 80:20 (v/v) trifluoroethanol:water, 97: 3 (w/w) trifluoroethanol:water, and 70:30 (v/v) ethanol:water. For com parison, rates of solvolysis of 2-adamantyl tosylate (2) have also bee n measured in 50:50, 80:20, and 90:10 (v/v) trifluoroethanol:water, an d for both compounds, activation parameters have been determined. Thes e and results published earlier allow a correlation of the two reactio ns and indicate that the in value for 2-adamantyl azoxytosylate solvol ysis is only 0.46. This is one of the lowest in values for a reaction that is unambiguously an S(N)1 solvolysis. We have also recorded the O -17 NMR spectrum of the 2-adamantyl tosylate formed from O-17-labelled 2-adamantyl azoxytosylate in deuteriochloroform, and the millimeter-w ave spectrum of the nitrous oxide evolved in the hydrolysis of O-18-la belled 2-adamantyl azoxytosylate. These labelling studies have provide d more detailed knowledge of the SN1 fragmentation mechanism of I and exclude a mechanism of reaction via rearrangement to N-(2-adamantyl),O -(p-toluenesulfonyl)hydroxylamine (5). Attempted deoxygenation of 1 to give 2-adamantyl diazotosylate (8) and a subsequent fragmentation pro ved unsuccessful.