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Organocatalytic reactions, enantioselection

Chiral N heterocyclic carbenes (NHCs), as Lewis basic organocatalysts, have been synthesized and applied to enantioselective organocatalytic reactions in recent years. Encouraged by Sheehan and Hunneman s first report of chiral thiazolium salts as NHC precursors for organocatalytic reactions [37], Leeper, Enders, Rovis, Glorius, Herrmann, and others have synthesized series of novel chiral NHCs with mono cyclic, bicyclic, or tricyclic backbones [38]. Recently, a series of bifunctional NHCs were synthesized and applied to aza BMH reaction of cyclopent 2 enone with... [Pg.418]

Electrophihcity The dark-side of indole chemistry 13OBC5206. Enantioselective organocatalytic reactions with isatin 13COC1957. Indoles in multicomponent processes 12CRV3508. [Pg.277]

In the late 1990s, several research groups worked on the development of chiral DMAP analogs. The works of Fu [23], Vedejs [24], and Fuji [25] led to the synthesis of powerful catalysts and the development of enantioselective organocatalytic reactions such as Steghch rearrangements, kinetic resolutions of secondary alcohols, kinetic resolution of amines, and so on (Scheme 1.8). [Pg.5]

Sparr, C., Gilmour, R. (2011). Cyclopropyl iminium activation reactivity umpolung in enantioselective organocatalytic reaction design. Angewandte Chemie International Edition, 50, 8391-8395. [Pg.361]

In contrast to the use of the specific type of sulfur ylides and related compounds, the employment of readily available alkyl halides for a catalytic Michael-alkylation reaction with enals to produce the corresponding formal [2-1-1] cycloadducts is an extremely challenging task. As an example, Wang [82a] and Cordova [82b, 83a] independently reported the enantioselective organocatalytic reaction of bromoma-lonates 78 and enals, which led to the corresponding cyclopropanes 79. In both cases, chiral diarylprolinol trimethylsilyl ethers 8 and 80 were involved as catalysts, giving access to the corresponding 2-formylcyclopropane derivatives 79 in... [Pg.1116]

An enantioselective organocatalytic 1,3-DC reaction, based on the activation of a,fi-unsaturated aldehydes through the reversible formation of iminium ions with chiral imidazolidinones 100, was described. Good levels of asymmetric induction and diastereocontrol were achieved (up to 94% ee and 94 6 dr) <00JA9874>. [Pg.223]

Enantioselective organocatalytic conjugate additions such as Michael and aldol reactions have been intensely studied under new catalysts. However, only a few organocatalyzed Michael reactions have been developed. The reaction involves construction of a new C-N bond that is very attractive for syntheses of molecules with biological properties. [Pg.151]

Highly enantioselective organocatalytic Mannich reactions of aldehydes and ketones have been extensively stndied with chiral secondary amine catalysts. These secondary amines employ chiral prolines, pyrrolidines, and imidazoles to generate a highly active enamine or imininm intermediate species [44], Cinchona alkaloids were previonsly shown to be active catalysts in malonate additions. The conjngate addition of malonates and other 1,3-dicarbonyls to imines, however, is relatively nnexplored. Snbseqnently, Schans et al. [45] employed the nse of Cinchona alkaloids in the conjngate addition of P-ketoesters to iV-acyl aldimines. Highly enantioselective mnltifnnctional secondary amine prodncts were obtained with 10 mol% cinchonine (Scheme 5). [Pg.152]

The first report of an enantioselective organocatalytic [3+2] cycloaddition between nitrones and a,P-nnsaturated aldehydes was reported by MacMillan and co-workers who showed that iminium ion activation was effective in this reaction (Scheme 8) [64], After a survey of seven catalysts the imidazolidinonium salt 12 HC10 emerged as the most efficient system. The reactions were conducted in a mixture of nitromethane and water at -20 °C in the presence of 20 mol% catalyst... [Pg.291]

Guillena G, Ramon DJ, Yus M (2007) Organocatalytic enantioselective multicomponent reactions (OEMCRs). Tetrahedron-Asymmetry 18 693-700... [Pg.269]

Interestingly, enantioselective alkylation reactions [64] were also developed using, for instance, Cu(OTf)2, [65], [Cu(SbF6)2, Zn(OTf)2] [66], Cu(C104)2-6H20 [67] or Sc (OTf)3 [68] in combination with diverse chiral ligands. Remarkably, organocatalytic alkylations of pyrroles, indoles and anilines by 3-phenylpropenal have been also developed [69]. [Pg.188]

The required chiral sulfur ylide of type 59 is formed in a reaction with a diazo compound in the presence of an achiral metal catalyst. Subsequently, asymmetric reaction of the chiral ylide 59 with the C=N double bond of the imine proceeds diastereoselectively and enantioselectively, giving the optically active aziridine 57. The chiral sulfide catalyst released is then used for the next catalytic cycle. The cat-alytically active species in the asymmetric process is the sulfide, so this concept can also be regarded as an organocatalytic reaction. [Pg.119]

In summary, several reports have shown that asymmetric modified aldol reactions using y-dienolates, nitroalkanes, or nitrones as donors can (in principal) be performed by use of organocatalysts. Often, however, enantioselectivity is moderate only, and must still be improved. Because these organocatalytic reactions give important intermediates, e.g. for synthesis of pharmaceuticals, it can be expected that this field of modified aldol reactions with organocatalysts will gain further synthetic importance in the future. [Pg.179]

A key step in the total synthesis of the marine metabolite (—)-solanopyrone D (161) is the enantioselective organocatalytic intramolecular Diels-Alder reaction of the trienal (158) to the decalin aldehyde (160) in the presence of the imidazolidinone catalyst (159) (Scheme 45).187 Protonated 1,2-diamino-1,2-diphenylethane has been... [Pg.381]

Another key event in the history of organocatalytic reaction was the discovery of efficient r-proline-mediated asymmetric Robinson annulation reported during the early 1970s. The so-called Hajos-Parrish-Eder-Sauer-Wiechert reaction (an intramolecular aldol reaction) allowed access to some of the key intermediates for the synthesis of natural products (Scheme 1.4) [37, 38], and offered a practical and enantioselective route to the Wieland-Miescher ketone [39]. It is pertinent to note, that this chemistry is rooted in the early studies of Langenbeck and in the extensive investigations work of Stork and co-workers on enamine chemistry... [Pg.5]

The direct enantioselective organocatalytic a-fluorination can also be performed with cinchona alkaloid derivatives as catalyst under phase-transfer reaction conditions [25]. The fluorination reaction by NFSI of / -ketoesters 21, readily enolizable substrates, generated a stereogenic quaternary C-F bond in high yields and with enantioselectivities up to 69% ee for the optically active products 26 (Eq. 6). [Pg.69]

Ahrendt KA, Borths CJ, MacMillan DWC (2000) New strategies for organic catalysis The first highly enantioselective organocatalytic Diels-Alder reaction. J Am Chem Soc 122 4243-4244 Akiyama T (2004) Preparation of chiral Bronsted catalysts in asym. synthesis and asym. Mannich, aza-Diels-Alder reaction, hydrophosphorylation therewith. PCT Int Appl WO 200409675, 2004-11-11... [Pg.35]

Brown SP, Goodwin NC, MacMillan DWC (2003b) The first enantioselective organocatalytic Mukaiyama-Michael reaction a direct method for the synthesis of enantioenriched gamma-butenolide architecture. J Am Chem Soc 125 1192-1194... [Pg.37]

Wilson RM, Jen WS, MacMillan DWC (2005) Enantioselective organocatalytic intramolecular Diels-Alder reactions. The asymmetric synthesis of solana-pyrone D. J Am Chem Soc 127 11616-11617 Xie JH, Zhou ZT, Kong WL, Zhou QL (2007) Ru-catalyzed asymmetric hydrogenation of racemic aldehydes via dynamic kinetic resolution efficient synthesis of optically active primary alcohols. J Am Chem Soc 129 1868-1869... [Pg.44]

Furthermore, many organocatalytic reactions are already known that proceed with both high conversion and enantioselectivity. There is a range of organocatalytic reactions known to give the desired products with excellent enantioselectivities of more than 99% ee (Berkessel and Groger 2005). [Pg.143]

Chen XH, Xu XY, Liu H, Cun LF, Gong LZ (2006) Highly enantioselective organocatalytic Biginelli reaction. J Am Chem Soc 128 14802-14803 Cordova A (2004) The direct catalytic asymmetric mannich reaction. Acc Chem Res 37 102-112... [Pg.246]

MacMillan DWC, Ahrendt KA, Borths CJ (2000) New strategies for organic catalysis the first highly enantioselective organocatalytic diels-Alder reaction. J Am Chem Soc 122 4243-4244... [Pg.318]

Catalytic enantioselective Mannich reactions provide one of the most versatile approaches for the synthesis of optically active chiral amines. Recently, several organocatalytic protocols have been developed using the parent cinchona alkaloids or their derivatives. [Pg.209]


See other pages where Organocatalytic reactions, enantioselection is mentioned: [Pg.332]    [Pg.183]    [Pg.183]    [Pg.332]    [Pg.183]    [Pg.183]    [Pg.77]    [Pg.315]    [Pg.321]    [Pg.340]    [Pg.443]    [Pg.273]    [Pg.39]    [Pg.166]    [Pg.269]    [Pg.271]    [Pg.275]    [Pg.397]    [Pg.453]    [Pg.115]    [Pg.116]    [Pg.36]    [Pg.63]    [Pg.140]    [Pg.329]    [Pg.118]    [Pg.99]    [Pg.2]    [Pg.101]   


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Amination reactions enantioselective organocatalytic

Cascade reactions enantioselective organocatalytic

Enantioselective reaction

Organocatalytic

Organocatalytic Enantioselective Biginelli Reactions

Organocatalytic Enantioselective Petasis-Type Reaction

Organocatalytic reactions, enantioselection Cinchona alkaloids

Organocatalytic reactions, enantioselection Friedel-Crafts alkylation

Organocatalytic reactions, enantioselection Henry reaction

Organocatalytic reactions, enantioselection catalytic cycle

Organocatalytic reactions, enantioselection enantioselectivity

Organocatalytic reactions, enantioselection enantioselectivity

Organocatalytic reactions, enantioselection phosphoric acids

Organocatalytic reactions, enantioselection protonation

Organocatalytic reactions, enantioselection reaction

Organocatalytic reactions, enantioselection reaction

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