A C<sub>2</sub>‐Symmetric Nickel Diamine Complex as an Asymmetric Catalyst for Enecarbamate Additions to Butane‐2,3‐dione.

Fossey, John S.; Matsubara, Ryosuke; Vital, Paulo; Kobayashi, Shū

doi:10.1002/chin.200603033

Cited by 2 publications

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“…Diketone 37 reacts with enecarbamates to afford stereogenic t-alcohols 38 in the presence of a nickel(II) triflate complex (Scheme 6). 26 Reactions of enecarbamates with azodicarboxylates 39 are catalyzed by a copper(II)-diamine 5e complex, leading to the formation of the adducts 40, with a high level of enantioselectivity (Table 7). 27 The initially formed acylimines 40A were readily converted into ketone products 40B after hydrolysis or 1,2-diamine derivatives 40C after highly stereoselective reduction by NaBH 4 .…”

Section: Miscellaneous Reactions Of Enamides and Enecarbamatesmentioning

confidence: 99%

“…Diketone 37 reacts with enecarbamates to afford stereogenic t- alcohols 38 in the presence of a nickel(II) triflate complex (Scheme ) . Reactions of enecarbamates with azodicarboxylates 39 are catalyzed by a copper(II)–diamine 5e complex, leading to the formation of the adducts 40 , with a high level of enantioselectivity (Table ) .…”

Section: Miscellaneous Reactions Of Enamides and Enecarbamatesmentioning

confidence: 99%

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Enamides and Enecarbamates as Nucleophiles in Stereoselective C–C and C–N Bond-Forming Reactions

2008

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Because the backbone of most of organic compounds is a carbon chain, carbon-carbon bond-forming reactions are among the most important reactions in organic synthesis. Many of the carbon-carbon bond-forming reactions so far reported rely on nucleophilic attack of enolates or their derivatives, because those nucleophiles can be, in general, readily prepared from the corresponding carbonyl compounds. In this Account, we summarize the recent development of reactions using enamide and enecarbamate as a novel type of nucleophile. Despite their ready availability and their intrinsic attraction as a synthetic tool that enables us to introduce a protected nitrogen functional group, enamide and enecarbamate have rarely been used as a nucleophile, since their nucleophilicity is low compared with the corresponding metal enolates and enamines. A characteristic of enamides and enecarbamates is that those bearing a hydrogen atom on nitrogen are relatively stable at room temperature, while enamines bearing a hydrogen atom on nitrogen are likely to tautomerize into the corresponding imine form. Enamides and enecarbamates can be purified by silica gel chromatography and kept for a long time without decomposition. During the investigation of nucleophilic addition reactions using enamides and enecarbamates, it has been revealed that enamides and enecarbamates bearing a hydrogen atom on nitrogen react actually as a nucleophile with relatively reactive electrophiles, such as glyoxylate, N-acylimino ester, N-acylimino phosphonate, and azodicarboxylate, in the presence of an appropriate Lewis acid catalyst. Those bearing no hydrogen atom on nitrogen did not react at all. The products initially obtained from the nucleophilic addition of enamides and enecarbamates are the corresponding N-protected imines, which can be readily transformed to important functional groups, such as ketones by hydrolysis and N-protected amines by reduction or nucleophilic alkylation. In the nucleophilic addition reactions of enamides and enecarbamates to aldehydes, it was unveiled that the reaction proceeds stereospecifically, that is, (E)-enecarbamate gave anti product and (Z)-enecarbamate afforded syn product with high diastereoselectivity (>97/3). This fact can be rationalized by consideration of a concerted reaction pathway via a hydrogen-involved cyclic six-membered ring transition state. In the addition reactions to N-acylimino phosphonates, much higher turnover frequency was observed when enamides and enecarbamates were used as a nucleophile than was observed when silicon enolates were used. When silicon enolates were used, the intermediates bearing a strong affinity for the catalyst inhibited catalyst turnover, resulting in low enantioslectivity because of the dominance of the uncatalyzed racemic pathway. In the case of nucleophilic addition of enamides and enecarbamate, however, a fast intramolecular hydrogen transfer from the enecarbamate nitrogen may prevent the intermediate from trapping the catalyst for a long time, to afford the product with a hig...

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Section: Miscellaneous Reactions Of Enamides and Enecarbamatesmentioning

confidence: 99%

Section: Miscellaneous Reactions Of Enamides and Enecarbamatesmentioning

confidence: 99%

Enamides and Enecarbamates as Nucleophiles in Stereoselective C–C and C–N Bond-Forming Reactions

2008

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“…Stilbenediamine containing metal complexes of copper, nickel and zinc have been catching attention due to their catalytic activity in asymmetric syntheses [2][3][4][5][6][7][8][9]. Recently achiral copper catalyst having dibenzoylstilbene as its ligand has been developed to achieve enantioselective Mannich-type reactions of Nacylimino esters with, for example, alkyl vinyl ethers to afford the corresponding N-acylated amino acid derivatives [7].…”

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confidence: 99%

Crystal structure of ethanolato-dibenzoylmethanato-(R,R-dibenzoylstilbenediamine)-nitratonickel(II), Ni(C2H5OH)(C15H11O2)(C28H26N2)(NO3)

Miyamoto¹,

Yajima²,

Horn³

et al. 2010

Zeitschrift Für Kristallographie - New Crystal Structures

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Source of materialThe title compound was prepared by adding 0.393 gofdibenzoylstilbenediamine (dbstien) obtained according to the published method [1] to 0.291 gofNi(NO 3 ) 2 · 6H 2 Odissolved in 10 ml of ethanol followed by the addition of 0.224 gofdibenzoylmethane and 0.07 go fK OH, and stirred for 60 minutes. The resulting bluish-green solution was filtered, allowed to stand. Green crystals suitable for X-ray diffraction experiments were obtained by slow vapour diffusion of diethyl ether into the ethanol solution. Experimental detailsThe hydrogen atoms bound to carbon atoms were fixed at calculated positions with d(C-H) =0.97 Å, d(C=C-H) =1.08 Å.The hydrogen bound to O6 was not located in the difference Fourier map due to the probable disorder over two sites. DiscussionStilbenediamine containing metal complexes of copper, nickel and zinc have been catching attention due to their catalytic activity in asymmetric syntheses [2][3][4][5][6][7][8][9]. Recently achiral copper catalyst having dibenzoylstilbene as its ligand has been developed to achieve enantioselective Mannich-type reactions of Nacylimino esters with, for example, alkyl vinyl ethers to afford the corresponding N-acylated amino acid derivatives [7]. To date, only af ew structures of these complexes have been reported, hence our interest to isolate, crystallize and to determine the molecular structure of the nickel complex presented here. The crystal structure consists of asymmetric units containing one Ni complex, [Ni(C 2H6O)(C15H11O2)(C28H28N2)(NO3)]. The central nickel atom has as lightly distorted octahedral coordination, with the angles around nickel ranging from 81.9(2)°to 103.1(2)°,and 172.8(2)°to 177.1(2)°,respectively. The average Ni-Ndistance (Ni-N2, Ni-N3) is 2.091(5) Å,which is in the normal bond range for an octahedral Ni complex. The respective Ni-O dbm distances Ni-O4 and Ni-O5 are 1.976(4) Å and 2.033(4) Å which reflect the relative trans effect exhibited by N3 as opposed to O6 (ethanol), making the former distance shorter. The nitrate molecule coordinates Ni at the expected distance Ni-O1 of 2.179(4) Å.T he dibenzoylstilbene and dibenzoylmethanate (dbm) bidentate chelate planes are virtually perpendicular to each other. The atomic arrangement around atoms C16 and C17 reflects the R,R configuration of dibenzoylstilbene of the overall absolute molecular structure. Finally, the oxygen of the ethanol molecule locates at the normal distance of 2.083(4) Å from the nickel centre.

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A C₂‐Symmetric Nickel Diamine Complex as an Asymmetric Catalyst for Enecarbamate Additions to Butane‐2,3‐dione.

Abstract: Butane-2,3-dione. -(FOSSEY, J. S.; MATSUBARA, R.; VITAL, P.; KOBAYASHI*, S.; Org. Biomol. Chem. 3 (2005) 16, 2910-2913; Grad. Sch. Pharm. Sci., Univ. Tokyo, Bunkyo, Tokyo 113, Japan; Eng.) -Nuesgen 03-033

Cited by 2 publications

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Enamides and Enecarbamates as Nucleophiles in Stereoselective C–C and C–N Bond-Forming Reactions

Enamides and Enecarbamates as Nucleophiles in Stereoselective C–C and C–N Bond-Forming Reactions

Crystal structure of ethanolato-dibenzoylmethanato-(R,R-dibenzoylstilbenediamine)-nitratonickel(II), Ni(C2H5OH)(C15H11O2)(C28H26N2)(NO3)

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A C2‐Symmetric Nickel Diamine Complex as an Asymmetric Catalyst for Enecarbamate Additions to Butane‐2,3‐dione.

Abstract: Butane-2,3-dione. -(FOSSEY, J. S.; MATSUBARA, R.; VITAL, P.; KOBAYASHI*, S.; Org. Biomol. Chem. 3 (2005) 16, 2910-2913; Grad. Sch. Pharm. Sci., Univ. Tokyo, Bunkyo, Tokyo 113, Japan; Eng.) -Nuesgen 03-033

Cited by 2 publications

References 1 publication

Enamides and Enecarbamates as Nucleophiles in Stereoselective C–C and C–N Bond-Forming Reactions

Enamides and Enecarbamates as Nucleophiles in Stereoselective C–C and C–N Bond-Forming Reactions

Crystal structure of ethanolato-dibenzoylmethanato-(R,R-dibenzoylstilbenediamine)-nitratonickel(II), Ni(C2H5OH)(C15H11O2)(C28H26N2)(NO3)

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A C₂‐Symmetric Nickel Diamine Complex as an Asymmetric Catalyst for Enecarbamate Additions to Butane‐2,3‐dione.