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The Effect of Leaving Group Orientation on Solvolytic Cope Rearrangements. A Study of exo -Tricyclo[4.4.1.1 2,5 ]dodeca-3,7,9-trien-11-yl Tosylates and Derivatives

1978; Oxford University Press; Volume: 51; Issue: 8 Linguagem: Inglês

10.1246/bcsj.51.2379

1348-0634

Shô Itô, Isamu Itoh, Yutaka Fujise, Tetsuo Nakatsu, Carol A. Senkler, Paul v. R. Schleyer,

Molecular spectroscopy and chirality

Synthesis and solvolytic behavior of derivatives of the highly hindered title compounds are described, exo-Tricyclo[4.4.1.12,5]dodeca-3,7,9-trien-syn-yl tosylate (syn-18-OTs) and the corresponding perhydro derivative, syn-23-OTs, solvolyze at rates that are in reasonable agreement with those predicted by Foote-Schleyer calculations.syn-18-OTs, and its dihydro derivatives, syn-19-OTs and syn-20-OTs, give completely rearranged products on solvolysis in acetic acid and 75% dioxane, 80% acetone, and 75% dioxane, respectively (Table 2). These products can be explained by normal cationic rearrangements, probably occurring after ionization. On the other hand, anti-18-OTs and anti-23-OTs solvolyze at rates ca. 102 times slower than those predicted by Foote-Schleyer calculations. Presumably the anti derivatives of 18-OTs, 20-OTs, 23-OTs, and the tetrahydro tosylate (22-OTs) suffer steric hindrance to ionization. Product formation from anti-18-OTs (Table 3) and anti-19-OTs in acetic acid and 75% dioxane, respectively, is explained as a [3s+3s] sigmatropic shift induced by ionization, with formation of an allylic ion providing the driving force for rearrangement.