134166-10-2Relevant academic research and scientific papers
Transition-metal aqua complexes of 4,6-dibenzofurandiyl-2,2'-bis(4- phenyloxazoline). Effective catalysis in Diels-Alder reactions showing excellent enantioselectivity, extreme chiral amplification, and high tolerance to water, alcohols, amines, and acids
Kanemasa, Shuji,Oderaotoshi, Yoji,Sakaguchi, Shin-Ichi,Yamamoto, Hidetoshi,Tanaka, Junji,Wada, Eiji,Curran, Dennis P.
, p. 3074 - 3088 (1998)
Cationic aqua complexes are prepared from a trans-chelating tridentate ligand, (R,R)-4,6-dibenzofurandiyl-2,2'-bis(4-phenyloxazoline) (DBFOX/Ph), and various transition-metal(II) perchlorates. These complexes are effective catalysts in the Diels - Alder reactions of cyclopentadiene with 3-alkenoyl- 2-oxazolidinone dienophiles and show excellent enantioselectivities. The active catalyst complex prepared from nickel(II) perchlorate hexahydrate has an octahedral structure with three aqua ligands, and it can be isolated and stored for months without loss of catalytic activity. Iron(II), cobalt(II), copper(II), and zinc(II) complexes are similarly active. The absolute configuration induced in the reaction can be readily predicted on the basis of the C2-symmetric structure of the complexes as well as the simple structure of the substrate complex. The aqua complex prepared from Ni(II) or Zn(II) perchlorate results in highly effective chiral amplification in the Diels-Alder reaction. Use of the DBFOX/Ph ligand of a low enantio purity of 20% ee leads to a 96% ee for the endo cycloadduct. Two mechanisms for amplification are involved in this remarkable chiral amplification: (1) precipitation of an S4-symmetric meso 2:1 complex between DBFOX/Ph and Ni(II) ion and (2) associative formation of 1:1 heterochiral complexes by the aid of hydrogen bonds based on aqua ligands to produce stable meso oligomers.
Asymmetric Diels-Alder Reaction of α,β-Unsaturated Oxazolidin-2-one Derivatives Catalyzed by a Chiral Fe(III)-Bipyridine Diol Complex
Li, Mao,Carreras, Virginie,Jalba, Angela,Ollevier, Thierry
supporting information, p. 995 - 998 (2018/02/23)
An asymmetric FeIII-bipyridine diol catalyzed Diels-Alder reaction of α,β-unsaturated oxazolidin-2-ones has been developed. Among various FeII/FeIII salts, Fe(ClO4)3·6H2O was selected as th
(1R)-(+)-camphor and acetone derived α′-hydroxy enones in asymmetric diels-alder reaction: Catalytic activation by Lewis and bronsted acids, substrate scope, applications in syntheses, and mechanistic studies
Banuelos, Patrcia,Garcia, Jesus M.,Gomez-Bengpa, Enrique,Herrero, Ada,Odriozola, Jose M.,Oiarbide, Mikel,Palomo, Claudio,Razkin, Jesus
supporting information; experimental part, p. 1458 - 1473 (2010/06/11)
Chemical Equation Presented The Diels-Alder reaction constitutes one of the most powerful and convergent C-C bond-forming transformations and continues to be the privileged route to access cyclohexene substructures, which are widespread within natural products and bioactive constituents. Over the recent years, asymmetric catalytic Diels-Alder methodologies have experienced a tremendous advance, but still inherently difficult diene-dienophile combinations prevail, such as those involving dienes less reactive than cyclopentadiene or dienophiles like β-substituted acrylates and equivalents. Here the main features of a'-hydroxy enones as reaction partners of the Diels-Alder reaction are shown, with especial focus on their potentials and limitations in solving the above difficult cases. α'-Hydroxy enones are able to bind reversibly to both Lewis acids and Bronsted acids, forming 1,4-coordinated species that are shown to efficiently engage in these inherently difficult Diels-Alder reactions. On these bases, a convenient control of the reaction stereocontrol can be achieved using a camphor-derived chiral α'-hydroxy enone model (substrate-controlled asymmetric induction) and either Lewis acid or Bronsted acid catalysis. Complementing this approach, highly enantio- and diastereoselective Diels-Alder reactions can also be carried out by using simple achiral α'-hydroxy enones in combination with Evans' chiral Cu(II)BOX complexes (catalyst-controlled asymmetric induction). Of importance, α'-hydroxy enones showed improved reactivity profiles and levels of stereoselectivity (endo/exo and facial selectivity) as compared with other prototypical dienophiles in the reactions involving dienes less reactive than cyclopentadiene. A rationale of some of these results is provided based on both kinetic experiments and quantum calculations. Thus, kinetic measurements of Bronsted acid promoted Diels-Alder reactions of α'-hydroxy enones show a first-order rate with respect to both enone and Bronsted acid promoter. Quantum calculations also support this trend and provide a rational explanation of the observed stereochemical outcome of the reactions. Finally, these fundamental studies are complemented with applications in natural products synthesis. More specifically, a nonracemic synthesis of (-)-nicolaioidesin C is described wherein a Brαnsted acid catalyzed Diels-Alder reaction involving a α'-hydroxy enone substrate is the key step toward the hitherto challenging tri substituted cyclohexene subunit.
Rational design of highly effective asymmetric Diels-Alder catalysts bearing 4,4-sulfonamidomethyl groups
Sakakura, Akira,Kondo, Rei,Matsumura, Yuki,Akakura, Matsujiro,Ishihara, Kazuaki
supporting information; experimental part, p. 17762 - 17764 (2010/03/25)
(Chemical Equation Presented) The rational design of bis(oxazoline)- copper(II) catalysts based on postulated intramolecular secondary n-cation interaction for the highly enantioselective Diels-Alder reaction is presented. A theoretical calculation sugges
Glyoxal bis-hydrazones: A new family of nitrogen ligands for asymmetric catalysis
Lassaletta, Jose M.,Alcarazo, Manuel,Fernandez, Rosario
, p. 298 - 299 (2007/10/03)
The introduction of C2-symmetric dialkylamino substructures in chiral non-racemic glyoxal bis-hydrazones such as 9 appears as the key design element for this novel ligand class, as shown in the highly enantioselective copper(II)-catalyzed Diels
Bis(oxazoline) and bis(oxazolinyl)pyridine copper complexes as enantioselective Diels-Alder catalysts: Reaction scope and synthetic applications
Evans, David A.,Barnes, David M.,Johnson, Jeffrey S.,Lectka, Thomas,Von Matt, Peter,Miller, Scott J.,Murry, Jerry A.,Norcross, Roger D.,Shaughnessy, Eileen A.,Campos, Kevin R.
, p. 7582 - 7594 (2007/10/03)
The scope of the Diels-Alder reaction catalyzed by bis(oxazoline) copper complexes has been investigated. In particular, [Cu((S,S)-t-Bu-box)](SbF6)2 (1b) has been shown to catalyze the Diels-Alder reaction between 3-propenoyl- 2-oxaz
Asymmetric Diels-Alder Reactions of an Acrylic Acid Derivative Using a Chiral Titanium Catalyst
Narasaka, Koichi,Tanaka, Hiroko,Kanai, Fumihiko
, p. 387 - 391 (2007/10/02)
Asymmetric Diels-Alder reactions of an acrylic acid derivative using a catalytic amount of a chiral titanium reagent were performed with several dienes.The titanium catalyst was prepared by the alkoxy exchange between dichlorodiisopropoxytitanium(IV) and a chiral 1,4-diol derived from (2R,3R)-tartrate.By the use of the titanium catalyst, the reaction between 3-acryloyl-1,3-oxazolidin-2-one and dienes proceeded in a toluene-petroleum ether mixture in the presence of Molecular Sieves 4A to afford the Diels-Alder adducts in 72-100percent yields and 88 - >96percent enantioselectivity.This reaction can be applied to a diene containing a hetero atom such as 2-ethylthio-1,3-butadiene, which affords the Diels-Alder adduct in a high optical purity.In this paper are also described the methods for determining the optical purities of the obtained 4-substituted 3-cyclohexenecarboxylic acid derivatives.
