Journal ArticleDOI
Chiral phosphine lewis bases catalyzed asymmetric aza-Baylis-Hillman reaction of N-sulfonated imines with activated olefins.
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TLDR
An effective bifunctional Lewis base and Bronsted acid phosphine Lewis base system has been disclosed in this catalytic, asymmetric aza-Baylis-Hillman reaction and the mechanistic insight has been investigated by 31P and 1H NMR spectroscopic measurements.Abstract:
In the aza-Baylis-Hillman reaction of N-sulfonated imines (N-arylmethylidene-4-methylbenzenesulfonamides and others) with methyl vinyl ketone, ethyl vinyl ketone, and acrolein, we found that, in the presence of a catalytic amount of chiral phosphine Lewis base such as (R)-2'-diphenylphosphanyl-[1,1']binaphthalenyl-2-ol LB1 (10 mol %) and molecular sieve 4A, the corresponding aza-Baylis-Hillman adducts could be obtained in good yields with good to high ee (70-95% ee) at low temperature (approximately -30 to -20 degrees C) or at room temperature in THF, respectively. In CH2Cl2 upon heating at 40 degrees C, the aza-Baylis-Hillman reaction of N-sulfonated imines with phenyl acrylate or naphthyl acrylate gave the adducts in good to high yields (60-97%) with moderate ee (52-77%). The mechanistic insight has been investigated by 31P and 1H NMR spectroscopic measurements. The key enolate intermediate, which has been stabilized by intramolecular hydrogen bonding, has been observed by 31P and 1H NMR spectroscopy. An effective bifunctional Lewis base and Bronsted acid phosphine Lewis base system has been disclosed in this catalytic, asymmetric aza-Baylis-Hillman reaction.read more
Citations
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Journal ArticleDOI
Organocatalyzed Baylis–Hillman reaction: an enantioselective approach
TL;DR: In this paper, a convenient protocol has been developed for the synthesis of Baylis-Hillman adducts in the presence of a base and an organocatalyst, based on hydrogen bonding using a pyrrolidine ring as the backbone.
Journal ArticleDOI
Intramolecular arene epoxidation by phosphadioxiranes.
Dong Zhang,Ruomei Gao,Shabana Afzal,Mario Vargas,Shantanu Sharma,Alison McCurdy,Muhammed Yousufuddin,Timothy Stewart,Robert Bau,Matthias Selke +9 more
TL;DR: Kinetic analyses show that all of the phosphadioxirane intermediate is converted to product, and this new intramolecular arene epoxidation reaction proceeds with complete retention of stereochemistry.
Journal ArticleDOI
Conversion of Dibenzoxaphosphinines into 2-Hydroxybiphenyl-2′-ylphosphane Ligands and Their BH3 Adducts: The O–Hδ+···Hδ––B Hydrogen–Hydrogen Bond
TL;DR: In this paper, the first report on hydrogen-hydrogen bonds in functionally substituted phosphane-boranes was given, which may explain the low reactivity at the OH group.
Journal ArticleDOI
Efficient Synthesis of 2-Methylene-3phosphorylalkanoates: Phosphorylation of Baylis–Hillman Bromides via an S N 2-S N 2′ Strategy
TL;DR: A novel synthesis of 2-methylene-3-phosphorylalkanoates under mild conditions is described, where Balyis–Hillman bromides react with secondary phosphine oxides or H-ph phosphonites in the presence of DABCO via an S N 2-S N 2′ protocol to produce the target compounds in good yields.
Journal ArticleDOI
Cooperative Trifunctional Organocatalysts for Proficient Proton Transfer Reactions.
Ryan Kenny,Fei Liu +1 more
TL;DR: This is an approach of developing and investigating trifunctional organocatalysts with three distinct catalytic functionalities, in order to understand how cooperativity could be organized for enantioselective activation that confers the observed proficiency in a tandem Michael-aldol-proton transfer elimination model reaction.
References
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Journal ArticleDOI
[(salen)Al]-Mediated, Controlled and Stereoselective Ring-Opening Polymerization of Lactide in Solution and without Solvent: Synthesis of Highly Isotactic Polylactide Stereocopolymers from Racemic d,l-Lactide
TL;DR: Easily accessible [(salen)(iPrO)Al] exerts excellent molecular-weight and stereochemical control in lactide polymerization either in solution or in the absence of solvent.
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Chiral Amine-Catalyzed Asymmetric Baylis−Hillman Reaction: A Reliable Route to Highly Enantiomerically Enriched (α-Methylene-β-hydroxy)esters
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Asymmetric Morita-Baylis-Hillman reactions catalyzed by chiral Brønsted acids.
TL;DR: The Brønsted-acid-catalyzed reaction is the first example of a highly enantioselective asymmetric MBH reaction of cyclohexenone with aldehydes.
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Development of bis-thiourea-type organocatalyst for asymmetric Baylis–Hillman reaction
TL;DR: A chiral bis-thiourea-type organocatalyst 2 developed for the Baylis-Hillman reaction provided a drastic rate enhancement in the case of cyclohexanecarboxaldehyde as discussed by the authors.
Journal ArticleDOI
β-Isocupreidine-Catalyzed Asymmetric Baylis−Hillman Reaction of Imines
TL;DR: A mechanistic proposal governed by hydrogen bonding is presented to give (S)-enriched N-protected-alpha-methylene-beta-amino acid esters, which shows the opposite enantioselectivity to the corresponding aldehydes.