91055-75-3Relevant academic research and scientific papers
Enantioselective organocatalytic hydride reduction
Ouellet, Stephane G.,Tuttle, Jamison B.,MacMillan, David W. C.
, p. 32 - 33 (2005)
The first enantioselective organocatalytic hydride reduction has been accomplished. The use of iminium catalysis has provided a new organocatalytic strategy for the enantioselective reduction of β,β-substituted αβ-unsaturated aldehydes to generate β-stereogenic aldehydes. The use of imidazolidinone 2 as the asymmetric catalyst has been found to mediate the transfer of hydrogen to a large class of enal substrates from ethyl Hantzsch ester. The capacity of catalyst 2 to accelerate E-Z isomerization prior to selective E-olefin reduction allows the implementation of geometrically impure enals in this operationally simple protocol. Copyright
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Scope and Mechanistic Studies
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
, p. 17500 - 17507 (2017/12/15)
Although iminium catalysis has become an important tool in organic chemistry, its combination with supramolecular host systems has remained largely unexplored. We report the detailed investigations into the first example of iminium catalysis inside a supramolecular host. In the case of 1,4-reductions of α,β-unsaturated aldehydes, catalytic amounts of host are able to increase the enantiomeric excess of the products formed. Several control experiments were performed and provided strong evidence that the modulation of enantiomeric excess of the reaction product indeed stems from a reaction on the inside of the capsule. The origin of the increased enantioselectivity in the capsule was investigated. Furthermore, the substrate and nucleophile scope were studied. Kinetic investigations as well as the kinetic isotope effect measured confirmed that the hydride delivery to the substrate is the rate-determining step inside the capsule. The exploration of benzothiazolidines as alternative hydride sources revealed an unexpected substitution effect of the hydride source itself. The results presented confirm that the noncovalent combination of supramolecular hosts with iminium catalysis is opening up new exciting possibilities to increase enantioselectivity in challenging reactions.
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
, p. 7698 - 7701 (2016/07/07)
The noncovalent combination of a supramolecular host with iminium organocatalysis is described. Due to cation–π interactions the reactive iminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented.
Hydride reduction of alpha, beta-unsaturated carbonyl compounds using chiral organic catalysts
-
Page/Page column 12, (2008/06/13)
Nonmetallic, chiral organic catalysts are used to catalyze the 1,4-hydride reduction of an α,β-unsaturated carbonyl compound. The α,β-unsaturated carbonyl compound may be an aldehyde or cyclic ketone, and the hydride donor may be a dihydropyridine. The reaction is enantioselective, and proceeds with a variety of hydride donors, catalysts, and substrates. The invention also provides compositions effective in carrying out the 1,4-hydride addition of α,β-unsaturated carbonyl compounds.
