Solvolysis of 2-Bicyclo[3.2.2]nonyl p-Toluenesulfonate. Evidence for the Formation of Classical Carbocation Intermediates

Abstract

The solvolysis rate of 2-bicyclo[3.2.2]nonyl p-toluenesulfonate (6-OTs) was nearly equal to that of cycloheptyl p-toluenesulfonate in 2,2,2-trifluoroethanol (TFE). This indicates that the ethylene bridge in 6-OTs does not significantly enhance the rate and that 6-OTs ionizes without anchimeric assistance. The solvolysis of [1-(13)C]-2-bicyclo[3.2.2]nonyl p-toluenesulfonate in methanol or TFE gave 2-substituted bicyclo[3.2.2]nonane, exo-2-substituted bicyclo[3.3.1]nonane, 2-bicyclo[3.2.2]nonene (10), and 2-bicyclo[3.3.1]nonene (11), whose distributions of (13)C labels were determined by quantitative (13)C NMR analysis using a relaxation reagent. The (13)C labels were exclusively placed at only two positions, the ratios of them were not unity, and the labels in 10 were less extensively scrambled than those in other products. These results indicate that the 2-bicyclo[3.2.2]nonyl cation is classical and that 10 is formed at a former ionization stage than 2-substituted bicyclo[3.2.2]nonane. The (13)C redistributions for both exo-2-substituted bicyclo[3.3.1]nonane and 11, which are yielded via 1,3-hydride shift, were similar to that of 2-substituted bicyclo[3.2.2]nonane, suggesting that 1,3-hydride shift occurs mainly at the solvent-separated ion pair.

Nature of the 2-Bicyclo[3.2.1]octanyl and 2-Bicyclo[3.2.2]nonanyl Cations

“…Okazaki et al reported the partial 13 C NMR chemical shifts and attached protons for their starting materials and products without giving assignments. Reference is made to the use of “authentic” samples without further details.…”

“…In a recently published study, Okazaki et al utilized carbon-13 labeling to study the solvolysis and rearrangement of 2-bicyclo[3.2.2]nonanyl tosylate in methanol and also 2,2,2-trifluoroethanol at 50 °C. They reported the formation of the ethers derived from the 2-bicyclo[3.2.2]nonanyl and 2-bicyclo[3.3.1]nonanyl systems.…”

13C NMR Spectroscopy for the Quantitative Determination of Compound Ratios and Polymer End Groups

“…To address the lower accuracy observed with some molecules containing aromatic carbons (3.4%), we added a paramagnetic relaxation agent. , For these studies, we employed a mixture of 3,5- and 2,5-dimethylphenol (Table ). Relaxation agents reduce longitudinal relaxation times, therefore improving quantitative 13 C NMR spectroscopic analysis. − Oxygen (O 2 ) was chosen to avoid sample contamination. Accuracy compared to 1 H NMR spectroscopic integration improved from 2.5% to 0.7% when the sample was prepared from solvent that was saturated with O 2 prior to sample preparation.…”

Different routes for the construction of biologically active diversely functionalized bicyclo[3.3.1]nonanes: an exploration of new perspectives for anticancer chemotherapeutics

“…During the solvolysis study of 2-bicyclo[3.2.2]nonyl p -toluenesulfonates, Okazaki's group and Schafaer's team found that the solvolysis products of such bicycles are usually enriched with bicyclo[3.3.1]nonanes. 221–224 It was found that when 477 was solvolyzed in methanol and 2,2,2-trifluoroethanol (TFE) buffered with 2,6-lutidine, 2-bicyclo[3.3.1]nonene ( 479 ) (yield 15–47%) and exo -2-R-bicyclo[3.3.1]nonane (R = methoxy, 480 ; R = trifluoroethoxy, 481 ) were formed along with other bicycles in 12–23% yield. The solvolytic data indicated that these products were formed from the 2-bicyclo[3.2.2]nonyl cation ( 478 ), thereby unveiling the evidences for the formation of a classical carbocation intermediate (Scheme 110).…”