20993-60-6Relevant academic research and scientific papers
Rhodium complex with unsymmetrical vicinal diamine ligand: excellent catalyst for asymmetric transfer hydrogenation of ketones
Deshpande, Sudhindra H.,Shende, Vaishali S.,Shingote, Savita K.,Chakravarty, Debamitra,Puranik, Vedavati G.,Chaudhari, Raghunath V.,Kelkar, Ashutosh A.
, p. 51722 - 51729 (2015/06/25)
New unsymmetrical vicinal diamine ligands with systematic variation in the regio and stereo positions in the amine and sulphonamide groups were synthesized from cheap starting material such as norephedrine. Catalytic Asymmetric Transfer Hydrogenation (ATH) of aromatic alkyl ketones has been investigated using transition metal complexes and new derivatives of monotosylated unsymmetrical vicinal diamine ligands using sodium formate as the hydrogen source, in water and methanol. Chiral secondary alcohols were obtained with excellent enantioselectivity (>95% ee) and conversion of ketones (>95%) with [Rh(Cp)Cl2]2 and ligand 4 as a catalyst. Enantioselectivity was found to be slightly higher with the use of methanol as a solvent for ATH of ketones with sodium formate as the hydrogen source compared to water as a solvent and was found to be consistent with all the ketones investigated. The reaction mixture is homogeneous in methanol unlike in water, where substrate and product are insoluble in water and form separate phase, sodium formate being soluble in water. The activity and enantioselectivity obtained for ATH of ketones using [Rh(Cp)Cl2]2 and unsymmetrical vicinal diamine ligand as catalyst was comparable with the C2 symmetric benchmark ligands like TsDPEN ((1R,2R)-N-(p-tolylsulfonyl)-1,2-diphenylethylene-diamine), and TsCYDN ((1R,2R)-N-(p-tolylsulfonyl)-1,2-cyclohexyl,diamine) under similar reaction conditions. To the best of our knowledge, this is first example of the ATH of ketones with good activity and high enantioselectivity with [Rh(Cp)Cl2]2 and unsymmetrical vicinal diamine ligands as catalyst systems.
Direct stereospecific synthesis of unprotected N-H and N-Me aziridines from olefins
Jat, Jawahar L.,Paudyal, Mahesh P.,Gao, Hongyin,Xu, Qing-Long,Yousufuddin, Muhammed,Devarajan, Deepa,Ess, Daniel H.,Kurti, Laszlo,Falck, John R.
, p. 61 - 65 (2014/03/21)
Despite the prevalence of the N-H aziridine motif in bioactive natural products and the clear advantages of this unprotected parent structure over N-protected derivatives as a synthetic building block, no practical methods have emerged for direct synthesis of this compound class from unfunctionalized olefins. Here, we present a mild, versatile method for the direct stereospecific conversion of structurally diverse mono-, di-, tri-, and tetrasubstituted olefins to N-H aziridines using O-(2,4-dinitrophenyl)hydroxylamine (DPH) via homogeneous rhodium catalysis with no external oxidants. This method is operationally simple (i.e., one-pot), scalable, and fast at ambient temperature, furnishing N-H aziridines in good-to-excellent yields. Likewise, N-alkyl aziridines are prepared from N-alkylated DPH derivatives. Quantum-mechanical calculations suggest a plausible Rh-nitrene pathway.
Asymmetric olefin aziridination using a newly designed Ru(CO)(salen) complex as the catalyst
Kim, Chungsik,Uchida, Tatsuya,Katsuki, Tsutomu
, p. 7188 - 7190 (2012/07/31)
Highly enantioselective and good to high-yielding aziridination of conjugated and non-conjugated terminal olefins and cyclic olefins was achieved using a newly designed Ru(CO)(salen) complex as the catalyst in the presence of SESN3 under mild conditions.
Efficient synthesis of cis-thiazolidinethiones derived from ephedrines
Cruz, Alejandro,Padilla-Martinez, Itzia I.,Garcia-Baez, Efren V.
, p. 394 - 398 (2011/06/11)
The reaction of chlorodeoxypseudoephedrine or chlorodeoxynorpseudoephedrine hydrochlorides with sodium dithiocarbonate in stirring ethanol at 0 °C to stereoselectively afford the corresponding cis-thiazolidinethiones in good yields (81% and 95%) is reported. The in situ formation of a cis-aziridine to explain the presence of trans-thiazolidinethione as a side product is proposed when the same reaction was carried out at room temperature. In addition, a 70:30 mixture of trans-isomers of a thiazolidinethione/isothiazolidinethione was formed when a cis-aziridine NH was reacted with carbon disulfide in refluxing ethanol. The analogous reaction with cis-aziridine N-Me stereoselectively affords the corresponding cis-thiazolidinethione. The 1H and 13C NMR data of the thiazolidinethiones were assigned. cis-3,4-Dimethyl-5-phenylthiazolidine-2-thione was crystallized from ethanol and its X-ray diffraction structure was analyzed.
A micellar iodide-catalyzed synthesis of unprotected aziridines from styrenes and ammonia
Varszegi, Csaba,Ernst, Martin,Van Laar, Frederik,Sels, Bert F.,Schwab, Ekkehard,De Vos, Dirk E.
, p. 1477 - 1480 (2008/12/22)
(Chemical Equation Presented) Aziridines from ammonia: Unprotected aziridines are formed from styrenes in one catalytic step. Ammonia is incorporated directly using an aqueous micellar solution containing bleach as oxidant and substoichiometric amounts of
New insights into the mechanism of palladium-catalyzed allylic amination
Watson, Iain D. G.,Yudin, Andrei K.
, p. 17516 - 17529 (2007/10/03)
A comparative investigation into palladium-catalyzed allylic amination of unsubstituted aziridines and secondary amines has been carried out. The use of NH aziridines as nucleophiles favors formation of valuable branched products in the case of aliphatic allyl acetates. The regioselectivity of this reaction is opposite to that observed when other amines are used as nucleophiles. Our study provides evidence for the palladium-catalyzed isomerization of the branched (kinetic) product formed with common secondary amines into the thermodynamic (linear) product. In contrast, the branched allyl products obtained from unsubstituted aziridines do not undergo the isomerization process. Crossover experiments indicate that the isomerization of branched allylamines is bimolecular and is catalyzed by Pd0. The reaction has significant solvent effect, giving the highest branched-to-linear ratios in THF. This finding can be explained by invoking the intermediacy of σ-complexes, which is consistent with NMR data. The apparent stability of branched allyl aziridines towards palladium-catalyzed isomerization is attributed to a combination of factors that stem from a higher degree of s-character of the aziridine nitrogen compared to other amines. The reaction allows for regio- and enantioselective incorporation of aziridine rings into appropriately functionalized building blocks. The resulting methodology addresses an important issue of forming quaternary carbon centers next to nitrogen. The new insights into the mechanism of palladium-catalyzed allylic amination obtained in this study should facilitate synthesis of complex heterocycles, design of new ligands to control branched-to-linear ratio, as well as absolute stereochemistry of allylamines.
Transition metal-catalyzed synthesis and reactivity of N-alkenyl aziridines
Dalili, Shadi,Yudin, Andrei K.
, p. 1161 - 1164 (2007/10/03)
(Chemical Equation Presented) Straightforward methods for palladium-catalyzed alkenylation of aziridines with alkenyl halides and copper-catalyzed alkenylation of aziridines with alkenyl boronic acids have been developed. This methodology offers attractive alternatives to the known methods requiring activated alkenyl halides and acetylenes. A wide variety of N-alkenyl aziridines containing substituents other than electron-withdrawing substituants such as cyano groups and sulfones have been synthesized in good yields. Furthermore, these N-alkenyl aziridines exhibit quite a different reactivity from conventional enamines, as demonstrated by their reactivity.
Funktionelle Phosphane: Part XI. Optisch reine β-Aminophosphane und β-Aminophosphinite für die komplexkatalysierte Reduktion organischer Carbonylverbindungen. Molekülstrukturen von [(1R,2R)-Ph2PCH(Ph)CH(Me)NH2Me]Cl, (1R,2S)-Ph2<
Dahlenburg, Lutz,G?tz, Rainer
, p. 88 - 98 (2007/10/03)
The preparation of optically active β-aminophosphane ligands, (-)-(1R,2S)-Ph2PCH(Ph)CH(Me)NH2 (5), (+)-(1S,2S)-Ph2PCH(Ph)CH(Me)NH2 (6), (-)-(1R,2R)-Ph2PCH(Ph)CH(Me)NHMe (7), and (1R,2S)-Ph2
Activation of manganese nitrido complexes by Bronsted and Lewis acids. Crystal structure and asymmetric alkene aziridination of a chiral salen manganese nitrido complex
Ho, Chi-Ming,Lau, Tai-Chu,Kwong, Hoi-Lun,Wong, Wing-Tak
, p. 2411 - 2413 (2007/10/03)
Styrene is readily converted to 2-phenylaziridine by salen manganese(v) nitrido complexes in the presence of Bronsted or Lewis acids such as F3CCO2H or BF3, the crystal structure of a chiral manganese nitrido complex that
N,N-DIHALOPHOSPHORAMIDES-XIV; TWO-STEP AMINOBROMINATION OF PHENYLETHYLENES AND α-OLEFINS WITH DIETHYL N,N-DIBROMOPHOSPHOROAMIDATE (DBPA)
Zawadzki, S.,Zwierzak, A.
, p. 2675 - 2681 (2007/10/02)
The addition of DBPA to several phenylethylenes and terminal olefins has been studied.The reaction was found to preceed in boiling dichloromethane and was spontaneously or photolytically initiated depending on the structure and reactivity of the reactants
