28925-55-5Relevant academic research and scientific papers
Comparative Substituent Effects of Tosyloxy, Benzyloxy, and Phosphoryloxy Substituents in Carbocation Formation. Acid-Catalized Hydration of Vinyl Tosylates, Benzoates, and 1,1-Ditosylates
Cox, Robin A.,Allister, Michael Mc,Roberts, Kenneth A.,Stang, Peter J.,Tidwell, Thomas T.
, p. 4899 - 4902 (1989)
Kinetc results for theacid-catalized hydration of alkenyl esters CH2=C(OX)R (X = Bz, Ts) and literature data for X = Ac and PO3Et2 are analyzed by the excess acidity method, and it is concluded that all the substrates react by the AdE2 mechanism of rate-limiting proton transfer to the double bond.Average substituent parameters ?p+ derived for the groups OBz, OAc, and OPO3Et2 of -0.18, -0.16, and -0.20, respectively, are similar and indicate these groups are modestly effective electron donors, while the average values of 0.08 for the OTs group indicates this to be a net electron withdrawing group.Hydrolysis of t-BuCH=C(OTs)2 requires much stronger acid; it has kH+/kD+ = 5.75 and a low slope of the rate versus acidity plot that is interpreted in terms of rate-limiting protonation of a substrate whose basic oxygens interact strongly with the acid solvent.
