340161-40-2Relevant academic research and scientific papers
Generation of quaternary stereocenters by asymmetric Michael reactions: Enamine regiochemistry as configuration switch
Kreidler, Burkard,Baro, Angelika,Frey, Wolfgang,Christoffers, Jens
, p. 2660 - 2667 (2007/10/03)
Regioselective enamine formation from cyclic β-diketones 1 is obtained by the appropriate choice of activating agent: Bronsted acid catalyzed condensation gives endocyclic enamines 3 as the thermodynamically favored products. Activation with Lewis acid BF
Regioselective formation of endo- and exo- cyclic enamines: Both enantiomeric products accessible by the same chiral auxiliary
Christoffers, Jens,Kreidler, Burkard,Oertling, Heiko,Unger, Sven,Frey, Wolfgang
, p. 493 - 496 (2007/10/03)
The copper-catalyzed conversion of exo-cyclic enamines 4a-c with methyl vinyl ketone (2) yields spirocyclic products 6a-c in a sequence of Michael and aldol reaction. The application of the chiral auxiliary L-valine diethylamide results in the formation o
Regioselective enamine formation from oxonia-boranuida-betaines and their application in asymmetric Michael reactions
Christoffers, Jens,Kreidler, Burkard,Unger, Sven,Frey, Wolfgang
, p. 2845 - 2853 (2007/10/03)
β-Diketonato borate betaines 2 are readily accessible by the reaction of β-dicarbonyl compounds 1 with BF3·OEt2. Reaction of borates 2 with L-valine diethylamide (3a) gives almost exclusively the exocyclic enamines 4 as the kinetic p
New auxiliaries for copper-catalyzed asymmetric Michael reactions: Generation of quaternary stereocenters at room temperature
Christoffers, Jens,Mann, Alexander
, p. 1014 - 1027 (2007/10/03)
Dialkyl amides of L-valine, L-isoleucine, and L-tert-leucine (2) are excellent chiral auxiliaries for the construction of quaternary stereocenters at ambient temperature. Enaminoesters 3, prepared from these auxiliaries 2 and Michael donors 1. undergo a copper-catalyzed asymmetric Michael reaction with methyl vinyl ketone (MVK, 4) to afford products 5 in 70-90% yield and 90-99% ee (enantiomeric excess). The exclusion of moisture or oxygen is not necessary. The auxiliaries 2 are readily available by standard procedures. After workup they can be recovered almost quantitatively.
