Solvolytic reactions of endo-bicyclo[3.2.1]oct-6-en-8-yl tosylate

Abstract

The rates of solvolysis of endo-bicyclo[3.2.1]oct-6-en-8-yl tosylate have been determined in acetic acid and ethanol-water mixtures. Product studies indicated that only products with the parent structure were formed. Both the results of product studies and interpretation of rate data support a significant amount of anchimeric assistance by the carbon-carbon double bond.the known ezzz/o-bicyclo[3.2.1]octan-8-ol.10 The nmr spectrum of 9 had absorptions at 4.13 (m, 2, CH=CH), 5.25 (t, 1, CHOAc), 7.48 (m, 2, bridgehead), 7.94 (s, 3, CH3), 8.20-9.08 (general absorption, 6, (CH2)3). At normal sweep width the vinyl region of 9(5) The synthesis and solvolytic behavior of a related compound, endobicyclo[3.2.1]octa-2,6-dien-8-yl tosylate, has been reported: G. Klump,

Photochemistry of two .beta.,.beta.'-epoxy ketones, 3-oxatricyclo[3.2.1.02,4]octan-8-one and 3-oxatricyclo[3.3.1.02.4]nonan-9-one. Intramolecular reactions of .alpha.,.beta.-unsaturated aldehydo ketenes

“…This aliquot was also stored at 4 °C. After removal of solvent, the spectra of the aliquot and the main reaction mixture (230 mg crude; 20-25% material loss during photolysis) both revealed the same new product, trans-2methoxycyclohex-3-ene-l-carboxylic acid (7), formed from opening of the ß-lactone: IR 3500-2500 (s), 1710 (s, br), 1644 (w), 1095 (m, br) cm-1; NMR 1.43-2.83 (m), 3.30 (s, 3 ), 4.0 (m), 5.70 (s with fine structure, 2 H), 9.70 (br s, 1 H; variable).…”

“…A sample of 8 (15 mg) was hydrogenated (100%) using the same conditions as for 10. The product was identified as methyl trans-2methoxycyclohexane-l-carboxylate (9), having IR and NMR spectra identical with an authentic sample4 prepared from methyl transcyclohexan-2-ol-l-carboxylate8 by treatment with diazomethane in the presence of boron trifluoride etherate: IR 2933 (s), 2856 (w), 2824 (w), 1738 (s), 1447 (w), 1428 (w), 1374 (w), 1358 (w), 1322 (w), 1258 (w), 1242 (m), 1188 (m), 1167 (m), 1121 (w), 1096 (m), 1033 (w), 989 (w), 925 (w) cm-1; NMR 0.95-2.45 (m, 9 H), 3.23 and 3.27 (overlapping s, 3 H, and m, 1 H, respectively), 3.60 A sample of methyl c ¡'s -2methoxy cy clohexane -1 -carboxy late was prepared in the same manner and was shown to be different (IR, NMR) from 9. exo-3-Oxatricyclo[3.3.1.02 '4]nonan-9-one (2). Bicyclo[3.2.1[oct-6-en-8-one9,10 (12; 1.0 g, 8.2 mmol crude) in methylene chloride (28 mL) was added to a cold (4 °C) solution of m-chloroperbenzoic acid (1.85 g, 9.0 mmol; 85% pure) in methylene chloride (42 mL) and stirred for 3 h at room temperature under nitrogen.…”

Stable carbocations. CXXVII. Cyclohexenyl and cyclopentenyl cations and their methylated derivatives

“…It is known that halonium ions are much more soluble in S02 than in S02C1F. 34 This may cause the different behavior in ionization of trans-1,2-dibromocyclohexane. A similar ion mixture was obtained when isomeric 1,4-dibromocyclohexanes were ionized in either SbF5-S02 or SbF5-FS03H-S02 solution at -60°, indicating that they both form similar ions.…”

Structural effects in solvolytic reactions. XIII. Effect of increasing electron demand on the rates of solvolysis of 1-arylcyclopent-3-en-1-yl and 1-arylcyclopentyl p-nitrobenzoates. Evidence for the absence of .pi.-participation

“…For example, in 1967 Hanack and Riedlinger reported that A2-cyclobutenylmethyl tosylate (15) undergoes hydrolysis to give cyclopent-3-en-l-ol (16) as the major product (eq l). 13 Further, 4-bromocyclopentene (5) unable to contribute to the resolution of the claim that there indeed is a 1,3 orbital interaction in the cyclopent-3-en-1 -yl system.…”

“…4 These results are in line with the conclusion that the degree of puckering in the cyclopentene ring and hence the distance between the -electron cloud of the double bond and the developing cationic center must be crucial in determining the overall effect of anchimeric assistance. 5 The importance of this steric requirement can be seen by comparing the homologous series of bicyclo[2.1.zi] compounds ( 6) where = 1-3 ( = 0 for cyclopentene). Thus in 1969 Masamune and co-workers6 reported that the ace-tolysis of exo-6-bicyclo[2.1.1 ]hex-2-en-6-yl tosylate ( 8) is 5 X 1016 times faster than that of exo-bicyclo[2.1.1]hex-6-yl tosylate (7) In 1955, Winstein et al noted that zznZz-7-norbornenyl tosylate (2) undergoes acetolysis 10" times faster than 7norbornyl tosylate (l).2 In 1971, Hess5 reported that the acetolysis of ezzz/o-bicyclo[3.2.1 ]oct-6-en-8-yl tosylate (10) was 1.9 X 105 times faster than that of endo-bicyclo[3.2.1]oct-8-yl tosylate (9) Clearly, the relative rates show a definite trend with the increase of the distance between the carbon-carbon double bond and the developing carbonium ion center.…”