164913-54-6Relevant articles and documents
Siloxy Esters as Traceless Activators of Carboxylic Acids: Boron-Catalyzed Chemoselective Asymmetric Aldol Reaction**
Fujita, Taiki,Kanai, Motomu,Mitsunuma, Harunobu,Sameera, W. M. C.,Yamane, Mina
supporting information, p. 24598 - 24604 (2021/10/14)
The catalytic asymmetric aldol reaction is among the most useful reactions in organic synthesis. Despite the existence of many prominent reports, however, the late-stage, chemoselective, catalytic, asymmetric aldol reaction of multifunctional substrates is still difficult to achieve. Herein, we identified that in situ pre-conversion of carboxylic acids to siloxy esters facilitated the boron-catalyzed direct aldol reaction, leading to the development of carboxylic acid-selective, catalytic, asymmetric aldol reaction applicable to multifunctional substrates. Combining experimental and computational studies rationalized the reaction mechanism and led to the proposal of Si/B enediolates as the active species. The silyl ester formation facilitated both enolization and catalyst turnover by acidifying the α-proton of substrates and attenuating poisonous Lewis bases to the boron catalyst.
Triazolium Carbene Catalysts and Stereoselective Bond Forming Reactions Thereof
-
Page/Page column 9, (2011/10/04)
Provided herein are triazolium carbine catalysts useful for asymmetric hydration, fluorination, and deuteration, and processes for their preparation. Also provided are synthetic reactions in which these catalysts are used, in particular, in stereoselective formation of carbon-chlorine, carbon-hydrogen, carbon-fluorine, and carbon-deuterium bonds.
A 4-hydroxypyrrolidine-catalyzed mannich reaction of aldehydes: Control of anti-selectivity by hydrogen bonding assisted by bronsted acids
Gomez-Bengoa, Enrique,Maestro, Miguel,Mielgo, Antonia,Otazo, Itziar,Palomo, Claudio,Velilla, Irene
experimental part, p. 5333 - 5342 (2010/10/03)
An anti-selective Mannich reaction of aldehydes with N-sulfonyl imines has been developed by using a 4-hydroxypyrrolidine in combination with an external Bronsted acid. The catalyst design is based on three elements: the ct-substituent of the pyrrolidine, the 4-hydroxy group, and the Bronsted acid, the combination of which is essential for high chemical and stereochemical efficiency. The reaction works with aromatic aldehydederived imines, which have rarely been employed in previously reported enamine-based anti-Mannich reactions. Additionally, both N-tosyl and N-nosyl imines can be successfully used and the Mannich adducts can be easily reduced or oxidized, and after N-deprotection the corresponding ss-amino acids and ss-amino alcohols can be obtained with good yields. The results also show that this ternary catalytic system may be practical in other enamine-based reactions.
Vinylaluminum addition to sulfinimines (N-sulfinyl imines). Asymmetric synthesis of anti-α-alkyl β-amino esters
Davis, Franklin A.,Qiu, Hui,Song, Minsoo,Gaddiraju, Narendra V.
experimental part, p. 2798 - 2803 (2009/08/08)
Addition of vinylaluminum NMO reagents to N-(p-toluenesufinyl)- and N-(2-methypropanesulfinyl)-derived sulfinimines gives N-sulfinyl aza-Morita-Baylis-Hillman products (dr ) 7:1 to 12:1) that result from addition of the reagent from the least hindered dir
Diastereoselective addition of imidazolidin-2-one controlled enolates to activated imines
Roos, Gregory H. P.,Balasubramaniam, Sundari
, p. 755 - 762 (2007/10/03)
Ephedrine-based imidazolidin-2-one chiral auxiliaries afford good syn stereoselectivity in the addition of their derived titanium enolates with an activated imine system. This provides entry into β-amino acid systems.
Synthesis of Optically Active β-Lactams by the Reaction of 2-Acyl-3-phenyl-l-menthopyrazoles with C=N Compounds
Kashima, Choji,Fukusaka, Kiyoshi,Takahashi, Katsumi
, p. 1559 - 1565 (2007/10/03)
The reaction of 1-acyl-3,5-dimethyIpyrazoles 1 with C=N compounds was kinetically controlled with syn stereoselectivity through a lithium enolate intermediate using lithium diisopropylamide. In contrast, the anti stereoselective reaction of 1 was caused b
Addition to activated imines of enolates from chiral N-acyloxazolidinones
Abrahams, Isaac,Motevalli, Majid,Robinson, Andrew J.,Wyatt, Peter B.
, p. 12755 - 12772 (2007/10/02)
The lithium and titanium enolates of N-acyloxazolidinones 1a-c add in their chelated forms to PhCH=NTs, to give stereoselectively the β-amino acid derivatives 3a-c and 4a-c. The relative configurations of the newly created chiral centres were established
