Homoenolization and H/D exchange in tricyclic ketones. Rearrangement via a γ-enolate

1981 ◽  
Vol 59 (24) ◽  
pp. 3379-3381 ◽  
Author(s):  
A. K. Cheng ◽  
A. K. Ghosh ◽  
I. (Tse) Sheepy ◽  
J. B. Stothers

Under homoenolization conditions (t-BuO−, t-BuOH, 185 °C), 7,7-dimethyltricyclo[3.2.1.02,4]octan-6-one (5) readily rearranges to 4,4-dimethyltricyclo[3.3.0.02,8]octan-3-one (6) which subsequently suffers reduction of the three-membered ring, presumably by electron transfer from the tert-butoxide anion for which some evidence has been obtained. The conversion of 5 to 6 constitutes one of very few examples of rearrangement via a γ-enolate. From reactions in tert-butyl alcohol-O-d1, deuterium incorporation at the several sites in 5 and 6 undergoing H/D exchange was directly monitored by 2Hmr spectroscopy; these results shed light on the stereochemistry of homoenolate formation and cleavage.


1989 ◽  
Vol 67 (2) ◽  
pp. 187-192
Author(s):  
Sriyawathie Peiris ◽  
J. B. Stothers ◽  
Shirley E. Thomas

The behavior of the endo and exo isomers of 7,7-dimethyltricyclo[3.2.2.02,4]nonan-6-one (9, 17) under strongly basic conditions (t-BuO−/t-BuOH/185 °C) has been examined. In both cases rearrangement to the corresponding 8,8-dimethyl-tricyclo[4.2.1.02,4]nonan-7-one (11, 18) was found, with the exo isomer reacting approximately 8 times faster. Experiments in tert-butyl alcohol-O-d1 were carried out to determine the specific sites, the relative rates, and the stereochemistry of deuterium incorporation in the initial ketones. Although H/D exchange occurs most readily at the cyclopropyl methylene carbon in the endo isomer, none of the rearrangement product expected to arise via γ-enolate formation was observed. The results for these ketones are compared with our earlier observations in the related [2.2.2], [3.2.1.0], and [3.3.1.0] systems. Keywords: homoenolization, tricyclic ketones, H/D exchange.





1993 ◽  
Vol 58 (5) ◽  
pp. 1001-1006 ◽  
Author(s):  
Oľga Vollárová ◽  
Ján Benko

The kinetics of oxidation of [Co(en)2SCH2COO]+ with S2O82- was studied in water-methanol and water-tert-butyl alcohol mixtures. Changes in the reaction activation parameters ∆H≠ and ∆S≠ with varying concentration of the co-solvent depend on the kind of the latter, which points to a significant role of salvation effects. The solvation effect on the reaction is discussed based on a comparison of the transfer functions ∆Ht0, ∆St0 and ∆Gt0 for the initial and transition states with the changes in the activation parameters accompanying changes in the CO-solvent concentration. The transfer enthalpies of the reactant were obtained from calorimetric measurements.



2021 ◽  
pp. 116913
Author(s):  
Márcio José da Silva ◽  
Diego Morais Chaves ◽  
Sukarno Olavo ferreira ◽  
Rene Chagas da Silva ◽  
Jose Balena Gabriel Filho ◽  
...  




1954 ◽  
Vol 46 (6) ◽  
pp. 59-59
Author(s):  
J Westwater ◽  
L Audrieth


Sign in / Sign up

Export Citation Format

Share Document