28115-07-3Relevant academic research and scientific papers
Synergistic interplay of a non-heme iron catalyst and amino acid coligands in H2O2 activation for asymmetric epoxidation of α-alkyl-substituted styrenes
Cuss, Olaf,Ribas, Xavi,Lloret-Fillol, Julio,Costas, Miquel
, p. 2729 - 2733 (2015)
Highly enantioselective epoxidation of α-substituted styrenes with aqueous H2O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97% ee) in short reaction times.
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 (2007/10/02)
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.
