1032509-62-8Relevant articles and documents
Stereoselective Koenigs–Knorr Glycosylation Catalyzed by Urea
Sun, Lifeng,Wu, Xiaowei,Xiong, De-Cai,Ye, Xin-Shan
, p. 8041 - 8044 (2016)
A stereoselective Koenigs–Knorr glycosylation reaction under the catalysis of urea is described. This method is characterized by urea-mediated hydrogen-bond activation and subsequent glycosylation with glycosyl chlorides or bromides. Excellent yields and high anomeric selectivity can be achieved in most cases. Moreover, the low α-stereoselectivity of glycosylations observed when using perbenzylated glucosyl donors can be greatly improved by the addition of tri-(2,4,6-trimethoxyphenyl)phosphine (TTMPP).
Metal-Free Deoxygenation of Chiral Nitroalkanes: An Easy Entry to α-Substituted Enantiomerically Enriched Nitriles
Pirola, Margherita,Faverio, Chiara,Orlandi, Manuel,Benaglia, Maurizio
, p. 10247 - 10250 (2021/06/18)
A metal-free, mild and chemodivergent transformation involving nitroalkanes has been developed. Under optimized reaction conditions, in the presence of trichlorosilane and a tertiary amine, aliphatic nitroalkanes were selectively converted into amines or nitriles. Furthermore, when chiral β-substituted nitro compounds were reacted, the stereochemical integrity of the stereocenter was maintained and α-functionalized nitriles were obtained with no loss of enantiomeric excess. The methodology was successfully applied to the synthesis of chiral β-cyano esters, α-aryl alkylnitriles, and TBS-protected cyanohydrins, including direct precursors of four active pharmaceutical ingredients (ibuprofen, tembamide, aegeline and denopamine).
A Continuous-Flow, Two-Step, Metal-Free Process for the Synthesis of Differently Substituted Chiral 1,2-Diamino Derivatives
Pirola, Margherita,Compostella, Maria Elena,Raimondi, Laura,Puglisi, Alessandra,Benaglia, Maurizio
supporting information, p. 1430 - 1438 (2018/02/09)
The enantioselective organocatalytic reduction of aryl-substituted nitroenamines was successfully performed under continuous-flow conditions. After a preliminary screening with a 10-μL microreactor, to establish the best reaction conditions, the reduction was scaled up in a 0.5-mL mesoreactor, without appreciable loss of enantioselectivity, that remained constantly higher than 90%. The in-flow nitro reduction was also accomplished, either by Raney nickel catalyzed hydrogenation or by a metal-free methodology based on the use of the very inexpensive and readily available reducing agent trichlorosilane. The final aim is to develop a two-step, continuous-flow process for the stereoselective, metal-free, catalytic synthesis of differently functionalized chiral 1,2-diamines.
New thiourea organocatalysts and their application for the synthesis of 5-(1H-indol-3-yl)methyl-2,2-dimethyl-1,3-dioxane-4,6-diones a source of chiral 3-indoylmethyl ketenes
Najda-Mocarska, Ewelina,Zakaszewska, Anna,Janikowska, Karolina,Makowiec, S?awomir
supporting information, p. 14 - 25 (2017/12/26)
The stereoselective properties of modified thiourea organocatalysts were tested in the Friedel–Crafts alkylation of indole with 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones, which produces chiral 5-((1H-indol-3-yl)(aryl)methyl)-2,2-dimethyl-1,3-dioxane-4,6-diones. Based on a tentative reaction mechanism for ((S)-N-benzyl-2-(3-(3,5-bis(trifluoromethyl)phenyl)thioureido)-N,3,3-trimethylbutanamide organocatalysts, modifications were applied in four selected regions. Systematic structure-stereoselectivity relationship study allowed designing the best efficient organocatalyst for the investigated Friedel–Crafts alkylation of indole with 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones.
Bifunctional Iminophosphorane Catalyzed Enantioselective Sulfa-Michael Addition to Unactivated α-Substituted Acrylate Esters
Farley, Alistair J. M.,Sandford, Christopher,Dixon, Darren J.
supporting information, p. 15992 - 15995 (2016/01/15)
The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated α-substituted acrylate esters catalyzed by a bifunctional iminophosphorane organocatalyst under mild conditions is described. The strong Br?nsted basicity of the iminophosphorane moiety of the catalyst provides the necessary activation of the alkyl thiol pro-nucleophile, while the two tert-leucine residues flanking a central thiourea hydrogen-bond donor facilitate high enantiofacial selectivity in the protonation of the transient enolate intermediate. The reaction is broad in scope with respect to the alkyl thiol, the ester moiety, and the α-substituent of the α,β-unsaturated ester, affords sulfa-Michael adducts in excellent yields (up to >99%) and enantioselectivities (up to 96% ee), and is amenable to decagram scale-up using catalyst loadings as low as 0.05 mol %.
Enantioselective catalytic addition of nitroesters to N-carboalkyloxy imines: a route to quaternary stereocenters
Puglisi, Alessandra,Raimondi, Laura,Benaglia, Maurizio,Bonsignore, Martina,Rossi, Sergio
supporting information; experimental part, p. 4340 - 4342 (2009/10/26)
A readily available, low cost bifunctional organic catalyst promoted the addition of nitroesters to imines; in the reaction between 2-nitropropionates and N-Boc protected aldehyde-imines the product bearing a new quaternary stereocenter was obtained in up
Stereoselective nucleophilic addition to imines catalyzed by chiral bifunctional thiourea organocatalysts
Puglisi, Alessandra,Benaglia, Maurizio,Annunziata, Rita,Rossi, Davide
experimental part, p. 2258 - 2264 (2009/04/04)
A new and easy synthesis of chiral bifunctional organic catalysts obtained by the combination of (S)-t-leucine-derivatives with (1R,2R)-trans-1,2-diamino-cyclohexane was developed. A few compounds, representatives of a class of organocatalysts containing a thiourea group and a tertiary amino group connected through a chiral backbone, have been successfully synthesized. The catalytic behaviour of such bifunctional chiral molecules, either neutral or protonated species, was investigated in the addition of acetylacetone to β-nitrostyrene as a model reaction. Using the best conditions, high yields and enantioselectivities of up to 85% were obtained. The same metal free catalysts were then employed in the addition of activated nucleophiles to imines: in the reaction of 1,3-diketones with N-CBz imines, the products were isolated in up to 61% ee, while in the reaction with diethyl malonate enantioselectivities up to 71% were reached.
Enantioselective thiourea-catalyzed additions to oxocarbenium ions
Reisman, Sarah E.,Doyle, Abigail G.,Jacobsen, Eric N.
, p. 7198 - 7199 (2008/12/21)
Asymmetric, catalytic reactions of oxocarbenium ions are reported. Simple, chiral urea and thiourea derivatives are shown to catalyze the enantioselective substitution of silyl ketene acetals onto 1-chloroisochromans. A mechanism involving anion binding by the chiral catalyst to generate a reactive oxocarbenium ion is invoked. Catalysts bearing tertiary benzylic amide groups afforded highest enantioselectivities, with the optimal structure being derived from enantioenriched 2-arylpyrrolidine derivatives. Copyright
Highly enantioselective aza-Baylis-Hillman reactions catalyzed by chiral thiourea derivatives
Raheem, Izzat T.,Jacobsen, Eric N.
, p. 1701 - 1708 (2007/10/03)
We report the discovery of asymmetric aza-Baylis-Hillman (ABH) reactions of N-p-nitrobenzenesulfonylimines with methyl acrylate catalyzed by chiral thiourea derivatives. A series of aromatic imines was found to undergo coupling with methyl acrylate with u
