99632-24-3Relevant academic research and scientific papers
Mechanisms of Elimination Reactions. 39. Steric and Electronic Effects on Stereochemistry in Eliminations from Primary Alkyltrimethylammonium Salts
Dohner, Brent R.,Saunders, William H. Jr.
, p. 245 - 247 (1986)
Percentages of syn elimination have been determined by high-field NMR on the products of elimination from R1R2CHCHDX.The results for X=OTs with t-BuO(-)/t-BuOH at 60 deg C were the following (R1, R2, percent syn): p-MeOC6H4, C6H5, 3.7; p-ClC6H4, C6H5, 29; p-ClC6H4, C6H5, 0 in EtO(-)/EtOH.For X=NMe3(+) with OH(-) in 50 molpercent Me2SO-50 molpercentH2O at 60 deg C, the results were as follows (R1, R2, percent syn): p-MeOC6H4, C6H5, 60; p-ClC6H4, C6H5, 72.For Ar(i-Pr)CHCHDNMe3(+) with OH(-) in 50 molpercent Me2SO-50 molpercent H2O at 80 deg C, the results were as follows (Ar, percent syn): m-ClC6H4, 78.6; p-ClC6H4, 69.5; C6H5, 59.6; p-EtC6H4, 58.3; p-t-BuC6H4, 60.5.Overall rates in this series were dissected into syn and anti rates, which fitted the Hammett equation to give ρsyn=3.69 +/- 0.20 and ρanti=3.02 +/- 0.22.This result supports the conclusion that syn elimination has a more carbanionic transition state than anti.The lower percent syn with X=OTs than with X=NMe3(+) is ascribed to the lesser steric requirements of OTs.
Acylation of aromatic substrates with ketenes. An example of vinyl oxocation reactivity.
Fountain, K.R.,Heinze, Pamela,Sherwood, Mark,Maddex, Dave,Gerhardt, Greg
, p. 1198 - 1205 (2007/10/02)
Acylations of aromatic substrates with ketenes involve the reactivity of species similar to vinyl cations.Resonance stabilization of ketene-aluminum chloride complexes seems to make these complexes less reactive than corresponding vinyl cations.The kinetic isotope effect of the reaction with dimethylketene and benzene is 1.06, compatible with vinylcation cases, but not with acylation with CH3COBF4 types of electrophiles.Substrate specificity was determined from k (toluene)/k (benzene) values.It was 47.2 for dimethylketene and 173.7 for diphenylketene.The diphenylketene-aluminum chloride complex could be isolated.
