21658-35-5Relevant academic research and scientific papers
Aromatic Claisen Rearrangements of Benzyl Ketene Acetals: Conversion of Benzylic Alcohols to (ortho-Tolyl)acetates
Burns, Jed M.,Krenske, Elizabeth H.,McGeary, Ross P.
, p. 252 - 256 (2017/01/24)
Claisen rearrangements of benzyl vinyl ethers are much less facile than those of aliphatic allyl vinyl ethers, and their synthetic utility has remained relatively unexplored. A one-pot procedure is reported for the generation and Claisen rearrangement of benzyl vinyl ethers that contain an activating α-alkoxy substituent on the vinyl group. A [3,3]-sigmatropic mechanism was supported by trapping of the intermediate isotoluene in an intramolecular Alder–ene reaction.
A water soluble dimeric steroid with catalytic properties. Rate enhancements from hydrophobic binding
Guthrie, J. Peter,Cossar, John,Dawson, Brian A.
, p. 2456 - 2469 (2007/10/02)
Dimeric steroids can be formed by reductive amination of terephthalaldehyde with 3-amino steroids using cyanoborohydride.An amino group in the 11 β-position can be blocked using a formyl group, and this can be removed by acid hydrolysis after dimerization.Trifluoroacetyl is not a suitable blocking group; although it can be removed by acid hydrolysis from monomeric steroids, it was only removed from the dimer under forcing conditions which caused degradation.The dimeric steroid is a catalyst for the hydrolysis of arylpropionate esters with good leaving groups.Acylation is markedly accelerated by hydrophobic binding of the aryl group of the substrate to the steroids.Rate enhancements, relative to imidazole, of up to 5.5 x 102 were obtained, and analysis of the data shows that the potential rate enhancement is 1.1 x 105.The magnitude of the hydrophobic binding is consistent with what was seen with earlier catalysts.Aggregation, even at very low concentrations, was a problem with anionic substrates.
Large hydrophobic interactions with clearly defined geometry. A dimeric steroid with catalytic properties.
Guthrie, J. Peter,Cullimore, Patricia A.,McDonald, Robert S.,O'Leary, Stella
, p. 747 - 764 (2007/10/02)
The steroid dimer α,α'-bis(17β-(4'-imidazolyl)-11-keto-5α-androstan-3β-amino)-p-xylene, 3, has been synthesized by reductive amination of 17β-(4'-imidazolyl)-5α-androstane-3,11-dione by p-xylenediamine in the presence of sodium cyanoborohydride, and by reductive amination of terephthalaldehyde by 3β-amino-17β-(4'-imidazolyl)-5α-androstan-11-one.The second method is stereochemically unambiguous; the first is not.Compound 3 acts as a catalyst for the hydrolysis of 3-arylpropionate esters of 3-hydroxy-4-nitrobenzoic acid.For the phenanthryl propionate the rateenhancement relative to imidazole is 200-fold, and the rate enhancement relative to the hypothetical rate for the propionate reacting with the steroid by the same transition state geometry is 3000-fold.The slope of a plot kkorr vs. ? for the reaction of 3b with aryl propionate ester was 0.83; the corresponding slope for 12 was 0.39.This provides a design parameter for the construction of artificial enzymes.
