Recombination of Carbocation–Sulfinate Ion Pairs

Abstract

again increases relative to 3 and as second product of the cycloreversion, the diazadistannetidine 5 begins to crystallize.On treatment of crystals of 3 with warmed toluene (ca. 60°C) a color change from red to yellow takes place and again a [2 + I] cyclore~ersion[~] yields stannylene 1 and stannanimine 4, which in agreement with the results of Wiberg and VasishtC6] dimerizes to 5. On reaction of 1 with 2 in the ratio 1 :3.5 the stannanimine is trapped almost quantitatively by 2 in a [2 + 31 cycloaddition to form 6.I6IThe result of the X-ray structure analysis['] of 3 is shown in Figure 1. Although the tin-nitrogen bond lengths lie with-Y Fig. 1. Structure of 3 in the crystal. Important bond lengths [A] and angles ["I:

Cooperative Binding of SO2 under M–O and C–S Bond Formation in a Rhenium(I) Complex with Activated Amino- or Iminopyridine Ligand

“…A few sulfinate esters were reported to rearrange via a reversible dissociation-recombination process. This rearrangement can either lead to sulfones or result in racemization; both pathways can proceed via an ion-pair intermediate. , In that context, the positive value of Δ S # for the interconversion of 2a/2b may hint toward a process different from simple pyramidal inversion. Single crystals suitable for X-ray diffraction analysis were obtained via recrystallization of 2ab from CH 2 Cl 2 / n -hexanes.…”

The 2‐norbornyl cation: a retrospective

“…[2e] Further cooling to À158°C freezes out the 6,2-hydride shift that converts 27 to 29 (E a~6 kcal/mol). Now the low-field 4-proton absorption splits into two 2-proton absorptions at δ6.75 (positions 1 and 2) and δ3.17 (position 6), while the high-field signal splits into absorptions at δ2.13 (four protons at positions 3 and 5) and δ1.37 (two protons at position 7). No further change in the NMR spectrum is effected at lower temperatures, and protons at positions 1 and 2 remain equivalent.…”

“…A clever racemization‐labeling experiment suggests that a close‐range order in ion pairs can provide discrimination between C(1) and C(2). Thus, solvolysis of 18 O‐labeled 2‐norbornyl p ‐toluenesulfinate 10 in trifluoroacetic acid at 25 °C or in formamide at 150 °C affords a threefold excess of label‐retained 11 in the “returned” mixture of enantiomers 11 and 12 …”

“…Thus, solvolysis of 18 O-labeled 2-norbornyl p-toluenesulfinate 10 in trifluoroacetic acid at 25°C or in formamide at 150°C affords a threefold excess of label-retained 11 in the "returned" mixture of enantiomers 11 and 12. [7] When activation energies for the generation of 2-norbornyl ion pairs are low, exo/endo product ratios can be affected. Ion pairs 15 and 16, from fragmentations of exo-and endo-2norbornyloxychlorocarbenes, 13 and 14, form with activation energies ≤4 kcal/mol and give significantly different distributions of exo-and endo-2-norbornyl chloride, norbornene and nortricyclene (cf.…”