28525-26-0Relevant academic research and scientific papers
The Feeble Nucleofugality of a Nitronate Leaving Group and its Enhancement by Ring Strain
Piras, Pier Paolo,Thomas, Patsy J.,Stirling, Charles J. M.
, p. 658 - 659 (1982)
The rank of a nitronate ion in activated alkene-forming elimination is low (+2.6); incorporation of the leaving group in a cyclopropane accelerates elimination so much that the E1cB)R-(E1cB)l borderline is traversed but the retro-Thorpe-Ingold effect nevertheless operates.
Methylenecyclopropanes in elimination and addition reactions: Quantification of the effects of strain
Volta, Luca,Stirling, Charles J. M.
scheme or table, p. 1508 - 1522 (2010/03/24)
The effect of strain in 1,2-elimination reactions that form methylenecyclopropanes has been evaluated for a series of leaving groups. The worse the leaving group, the greater is the inhibitory effect of strain build-up, which reaches 50% of the excess enthalpy differential for the poorest leaving group studied. In nucleophilic addition to an electrophilic methylenecyclopropane, comparison of strained and unstrained systems shows that about 60% of the excess enthalpy differential promotes the reactivity of the strained system.
2-Bromoethyl glycosides for synthesis of glycoconjugates on solid support
Ellervik, Ulf,Jacobsson, M?rten,Ohlsson, J?rgen
, p. 2421 - 2429 (2007/10/03)
2-Bromoethyl glycosides can easily and in high yields be transformed into sulfones by treatment with a suitable thiol followed by oxidation with mCPBA. The observation that the so formed sulfones were cleaved by treatment with NaOMe/MeOH was used to desig
Elimination and Addition Reactions. Part 41. Nucleophilic Eliminative Fission of Cyclopropanes: the Coiled Spring Effect of Ring Strain on Nucleofugality and its Evaluation
Hughes, Simon,Griffiths, Gwerydd,Stirling, Charles J. M.
, p. 1253 - 1264 (2007/10/02)
Rates have been measured of sulphonyl-activated eliminative ring fissions of a series of six cyclopropanes in which the leaving group is stabilised by alkoxycarbonyl, cyano, or sulphonyl groups.The measurements allow assignment of ranks (nucleofugalities) to carbon leaving groups in systems in which the connection to the leaving group is strained by incorporation in a cyclopropane ring.The values obtained are compered with those obtained for a unstrained (acyclic) analogues.Rank enhancements of about 9(log) units are obtained; these enhancements suggests that free energies of activation for leaving-group expulsion are reduced by about 53 kJmol-1, or about 46 percent of these excess of enthalpy of the strained ring, notwithstanding the small degree of ring fission in the transition structure.The effect of phenyl substitution at the leaving group suggests that cleavage of the ring is very little advanced in the transition structure, although this is variable with the nature of the leaving-group stabilisation.This is the first direct determination of the effect of strain on nucleofugality.
