Iron(III) 2-ethylhexanoate as a novel, stereoselective hetero-Diels–Alder catalyst

Metal 2-ethylhexanoates and related compounds as useful precursors in materials science

“…Medium sized metal alkanoates, especially 2-ethylhexanoates have been extensively used, either alone or in combination with other complexes, as homogeneous catalysts for a variety of reactions. [112][113][114][115][116][117][118][119][120][121][122][123][124] Nickel(II) 2-ethylhexanoate is used as starting material for the preparation of Ziegler nickel catalysts, 112 whereas a 2 : 1 combination of ascorbic acid 6-palmitate and iron(III) 2-ethylhexanoate has been shown to be a very good catalyst for oxidation and oligomerization of ethyl linoleate, a model compound for alkyd resins. 113 Iron(III) 2-ethylhexanoate has also been used as a novel, mild Lewis acid catalyst for the stereoselective Diels-Alder reaction of ethyl (E)-4-oxobutanoate with alkyl vinyl ethers (alkyl = ethyl, isobutyl, n-butyl) to stereoselectively produce cis-2-alkoxy-3,4-dihydro-2H-pyran-4-carboxylic acid, ethyl esters with diastereoisomeric excesses (de) in as high as 98% yield.…”

Reinvestigation of “Single‐Crystal X‐ray Structure of 1,3‐dimethylcyclobutadiene”

“…Zudem wirkt das im zehnfachen Überschuss als Oxidationsmittel für das Hydrochinon 9 verwendete Eisenchlorid möglicherweise als Lewis‐Säure, die die nachfolgende IMDA‐Reaktion durch Polarisierung der Carbonyl‐π‐Bindungen in der Chinonzwischenstufe katalysiert 10. Außerdem würde die hohe, substratabhängige Diastereoselektivität (durch HPLC‐Messungen wurden weniger als 3 % eines epimeren Nebenprodukts nachgewiesen) die Notwendigkeit einer Diels‐Alderase in einem hypothetischen Biosyntheseweg für Elisabethin A ausschließen 11.…”

Elisabethin A: A Marine Diterpenoid Yet To Surrender to Total Synthesis

“…Secondly, the tenfold excess of iron chloride, employed as the oxidizing agent for hydroquinone 9 , might also act as a Lewis acid to catalyze the subsequent IMDA reaction through polarization of the carbonyl π bonds in the transient quinone 10. Moreover, the observed high substrate‐dependent diastereoselectivity, as confirmed by the HPLC detection of less than 3 % of an alleged minor epimer, would rule out the necessity for a Diels–Alderase in a hypothetical biosynthetic pathway to elisabethin A 11.…”